অন= 2497;শীলনী 2.5
1.তলৰ পূ= 2544;ণফল কে= 2439;টা নি= 2544;্ণয় কৰ= 2495;বলৈ উপ= 2479;ুক্ত ৰা= 2486;ি ব্= 2479;ৱহাৰ কৰ= 2494;ঃ�
(i) (x + 4)(x + 10)
সমাধা=
;নঃ
(x + 4)(x + 10)
=3D x2 + (4 + 10)= x + 40�10
=3D x2 + 14x + 40
(ii) (x + 8)(x � 10)
সমাধা=
;নঃ
�(x + 8)(x = � 10)
=3D x2 + {8 + (� 10)}x + 8�(� 10)
=3D x2 + (8 � 10)x � 80
=3D x2 � 2x � 80
(iii)
(3x + 4)(3x � 5)
সমাধা=
;নঃ
�(3x + 4)(3x � 5)
=3D (3x)2 + {4 + ( � 5)}3x + 4�( � 5= )
=3D 9x2 + (4 � 5)3x � 20
=3D 9x2 � 3x � 20
(iv)
সমাধা=
;নঃ
(v)
(3 � 2x)( 3 + 2x)
সমাধা=
;নঃ
(3 � 2x)( 3 + 2x)
=3D
32 � (2x)2
=3D
9 � 4x2
2. প্ৰত্যক্ষভাৱে পূৰণ=
span>
নõ=
3;ৰি
তø=
2;ৰ
পù=
8;ৰণফলসমূহ
নù=
5;ৰ্ণয়
কþ=
4;াঃ �
(i) 103 =
� 107
সমাধা=
নঃ
103 � 107
=3D (100 + =
3)(100 + 7)
=3D (100)2
+ (3 + 7)100 + 3�7
=3D 10000 +=
10�100 +
21
=3D 10000 +=
1000 + 21
=3D 11021
(ii) 95�=
96
সমাধা=
নঃ
95�96
=3D (100 � =
5)(100 � 4)
=3D 1002 +
{(� 5) + (� 4)}100 + (� 5)(� 4)
=3D 10000 +=
(� 5 �
4)100 + 20
=3D 10000 +=
(� 9)100
+ 20
=3D 10000 �=
900 + 20
=3D 9120
(iii) 10=
4�96
সমাধা=
নঃ
104�96
=3D (100 + =
4)(100 � 4)
=3D (100)2
� 42
=3D 10000 �=
16
=3D 9984
3. উপযুক=
্ত অভেদ ব্=
;যৱহাৰ কৰি উৎপাদ=
ক
বù=
5;শ্লেষণ
কþ=
4;াঃ �
(i) 9=
x2
+ 6xy + y2
সমাধা=
নঃ
9x2
+ 6xy + y2
=3D (3x<=
/i>)2
+ 2�3x � y + y2
=3D (3x<=
/i> + y)2
=3D (3x<=
/i> + y)(3x
+ y)
(ii) 4y2
� 4y + 1
সমাধা=
নঃ
4y2
� 4y + 1
=3D (2y<=
/i>)2
� 2�2y�1 + 12
=3D (2y =
� 1)2
=3D (2y =
� 1)(2y
� 1)
(iii)
সমাধা=
নঃ
4. উপযুক্ত অভেদ=
span>
বú=
9;যৱহাৰ কৰি=
b>
তø=
2;ৰ
ৰù=
4;শিবোৰ
বù=
5;স্তাৰ
কþ=
4;া।
(i) (=
x +
2y + 4z)2
সমাধা=
নঃ
(x +=
2y
+ 4z)2
�=3D x2 + (2y)2
+ (4z)2 + 2.x.(2y) + 2(2y)(4z=
) + 2(4z)x
�=3D x2 + 4y2
+ 16z2 + 4xy + 16yz + 8xz
(ii) (2<=
i>x
� y + 2)2
সমাধা=
নঃ
(2x =
� y
+ 2)2
�=3D (2x)<=
sup>2
+ (�y) 2 + z2 + 2�2x(� y) + 2(� y)z
+ 2�z�2x
�=3D 4x
(iii) (� 2x=
+ 3y
+ 2z)2
সমাধা=
নঃ
�(� 2x + 3y + 2z)
�=3D (� 2x=
)2
+ (3y)2 + (2z)2 + 2( � 2x)3y<=
/i>
+ 2�3y�2z + 2�2z(� 2x)
�=3D 4x
(iv) (3<=
i>a
� 7b � c)2
সমাধা=
নঃ
(3a =
� 7b
� c)2
=3D {3a<=
/i> + (� 7b)
+ (� c)}2
=3D (3a<=
/i>)2
+ ( � 7b)2 + ( � c)2 + 2�3a(� 7<=
i>b)
+ 2(� 7b)(� c) + 2(� c)3a
=3D 9a=
i>2
+ 49b2 + c2 � 42ab + 14bc=
� 6ca
(v) (� 2=
x
+ 5y � 3z)2
সমাধা=
নঃ
(� 2x + 5y
� 3z)2
=3D {(� 2x) +
5y + (� 3z)}2
�=3D (� 2x)2 + (5y=
i>)2
+ (� 3z)2 + 2( � 2x)(5y) + 2(5y)(� 3=
z)
+ 2(� 3z)(2x)
�=3D 4x2 + 25y2
+ 9z2 � 20xy � 30yz + 12zx
(vi)
সমাধা=
নঃ
5. উৎপাদক=
span> বিশ্=
2482;েষণ
কþ=
4;াঃ
(i) 4=
x2
+ 9y2 + 16x2 + 12xy � 2yz=
�
16xz
সমাধা=
নঃ
4x2
+ 9y2 + 16x2 + 12xy � 2yz=
�
16xz
=3D (2x<=
/i>)2
+ (3y)2 + (� 4z)2 + 2(2x).(3y=
)
+ 2(3y)(� 4z) + 2(2x)(� 4z)
=3D (2x<=
/i> + 3y
� 4z)2
=3D (2x<=
/i> + 3y
� 4z)(2x + 3y � 4z)
(ii)
সমাধা=
নঃ
6. তলৰ ঘনকেই=
টা বিস্তাৰ কৰাঃ
(i) (2x +
1)3
সমাধা=
নঃ
=3D (2x<=
/i>)3
+ 3(2x)2�1 + 3�2x�12 + 13
=3D 8x=
i>3
+12x2 + 6x + 1
(ii) (2<=
i>a
� 3b)2
সমাধা=
নঃ
(2a =
� 3b)2
=3D (2a<=
/i>)3
� 3(2a)2( 3b) + 3(2a)( 3b)2 �
(3b)3
=3D 8a=
i>3
� 36a2b + 54ab2 � 27b3
(iii)
সমাধা=
নঃ
(iv)
সমাধা=
নঃ
7. উপযুক্ত অভেদ ব্=
;যৱহাৰ কৰি তলৰ=
ৰাশিৰ মা=
;ন নিৰ্ণয় কৰ=
;াঃ
(i) (99)3
সমাধা=
নঃ
(ii) (102)3
সমাধা=
নঃ
(iii) (998)3
সমাধা=
নঃ
8. তলৰ
উû=
0;পাদক
বù=
5;শ্লেষণ
কþ=
4;াঃ �
(i) 8=
a3
+ b3 + 12a2b + 6ab2<=
/sup>
সমাধা=
নঃ
8a3
+ b3 + 12a2b + 6ab2<=
/sup>
=3D (2a<=
/i>)3
+ b3 + 3(2a)2b + 3(2a) b2
=3D (2a<=
/i> + b)3
=3D (2a<=
/i> + b)(2a
+ b)(2a + b)
(ii) 8a3
� b3 � 12a2b + 6ab2<=
/sup>
সমাধা=
নঃ
8a3
� b3 � 12a2b + 6ab2<=
/sup>
=3D (2a<=
/i>)3
+ b3 � 3(2a)2b + 3(2a) b2
=3D (2a<=
/i> � b)3
=3D (2a<=
/i> � b)(2a
� b)(2a � b)
(iii) 27=
� 125a3
� 135a + 225a2
সমাধা=
নঃ
27 � 125=
a3
� 135a + 225a2
=3D (3)3 �
(5a)3 � 3�32�5a + 3�3(5a)2<=
/sup>
=3D (3 � 5<=
i>a)3
=3D (3 � 5<=
i>a)(3
� 5a)(3 � 5a)
(iv) 64<=
i>a3
� 27b3 � 144a2b + 108ab2
সমাধা=
নঃ
64a<=
sup>3
� 27b3 � 144a2b + 108ab2
=3D (4a<=
/i>)3
� (3b)3 � 3(4a)2(3b) + 3(4a=
i>)(3b)2
=3D (4a<=
/i> � 3b)3
=3D (4a<=
/i> � 3b)(4a
� 3b)(4a � 3b)
(v)
সমাধা=
নঃ
9. সত্যাপন কৰাঃ �
(i) x3=
+ y3
=3D (x + y)(x2 � xy + y2=
)
সমাধা=
নঃ
R.H.S =3D (=
x +
y)(x2 � xy + y2)
=3D x(x2
� xy + y2) + y(x2 � xy=
+ y2)
=3D x3
� x2y + xy2 + x2y
� xy2 + y3
=3D x3
+ y3
=3D LHS
(ii) x3 � y3
=3D (x � y)(x2 + xy + y2=
)
সমাধা=
নঃ
R.H.S =3D (=
x �
y)(x2 + xy + y2)
=3D x(x2
+ xy + y2) � y(x2 + xy=
+ y2)
=3D x3
+ x2y + xy2 � x2y
� xy2 � y3
=3D x3
� y3
=3D LHS
10. উৎপাদক=
span> বিশ্=
2482;েষণ
কþ=
4;াঃ �
(i) 27y3 +
125z3
সমাধা=
নঃ
27y<=
sup>3
+ 125z3
�=3D (3y)3 + (5z=
)3
�=3D (3y + 5z){(3y)<=
sup>2
� (3y)(5z) + (5z)2}
�=3D (3y + 5z)(9y2 � 15=
yz
+ 25z2)
(ii) 64<=
i>m3
� 343n3
সমাধা=
নঃ
64m<=
sup>3
� 343n3
=3D (4m<=
/i>)3
� (7n)3
=3D (4m<=
/i> � 7n){(4m)2
+ (4m)(7n) + (7n)2}
=3D (4m<=
/i> � 7n)(16m2
+ 28mn + 49n2)
11. 27x3
+ y3 + z3 � 9xyz <=
span
lang=3DBN style=3D'font-size:12.0pt;font-family:Kalpurush;mso-ascii-font-fa=
mily:
"Times New Roman";mso-hansi-font-family:"Times New Roman";mso-bidi-language:
BN'>ৰ উৎপাদক
বù=
5;শ্লেষণ
কþ=
4;াঃ �
সমাধা=
নঃ
27x3 + y3 + z3
� 9xyz
�=3D (3x)3 + y3
+ z3 � 3(3x).y.z=
p>
�=3D (3x + y + z){(3=
x)2
+ y2 + z2 � (3x)(y) � =
yz
� z(3x)}
�=3D (3x + y + z)(9<=
i>x2
+ y2 + z2 � 3xy � yz � 3<=
i>xz)
12. সত্যাপন কৰা=
যে
সমাধা=
নঃ
13.(i) <=
/span>যদি x<=
/span> + y + z =3D 0 তেন্তে=
span> দেখু=
2451;ৱা যে=
;
x<=
span
style=3D'font-size:12.0pt'>3 +
y3 + z3 =3D 3xyz
সমাধা=
নঃ
আমি জা=
;নো যে=
;,=
x=
3 =
+ y3
+ z3 � 3xyz =3D� (x + y + z)(x2 + y2 =
+ z2
� xy � yz � zx)
⇒ x3 + y3 + <=
i>z3
� 3xyz =3D 0(x2 + y2 + =
z2
� xy � yz � zx) ���������=
�� [⸪x
+ y + z =3D 0]
⇒ x3 + y3 + <=
i>z3
� 3xyz =3D 0
⇒ x3 + y3 + <=
i>z3
=3D 3xyz
(ii) যদি =
a + b
+ c =3D 0 তেন্ত=
ে
দú=
3;খুওৱা যে,
�a2(b
+ c) + b2(c + a) + c2(a
+ b) + 3abc =3D=
span> 0
সমাধা=
নঃ
দিয়া আছ=
;ে,
a=
+ b + c =3D 0
⇒ a + b =3D � c
a= + b + c =3D 0<= o:p>
⇒ b + c =3D � a
a= + b + c =3D 0<= o:p>
⇒ a + c =3D � b
L.H.S =3D <=
i>a2(b
+ c) + b2(c + a) + c2(a
+ b) + 3abc
��������� =3D a2(� a=
) + b2
(� b) + c2 (� c) + 3abc
��������� =3D � a3 � b3
� c3 + 3abc
��������� =3D � (a3 + <=
i>b3
+ c3 � 3abc)
��������� =3D � (a + b + c)(a2
+ b2 + c2 � ab � bc � =
ca)
��������� =3D � 0(a2 + =
b2
+ c2 � ab � bc � ca)�������������������������������� [⸪=
a
+ b + c =3D 0]
��������� =3D 0
��������� =3D RHS
(iii) =
span>যদি 2a=
�
b + c =3D 0 তেন্ত=
ে
দú=
3;খুওৱা 4a2 � b2 + <=
i>c2
+ 4ac
সমাধা=
নঃ
দিয়া আছ=
;ে,
2a �=
b
+ c =3D 0
⇒ 2a + c =3D b
এতিয়া,
LHS =3D 4a2 �=
b2
+ c2 + 4ac
=3D 4a=
i>2
� (2a + c)2 + c2 + 4ac
=3D 4a=
i>2
� {(2a)2 +2(2a)c + c2} + =
c2
+ 4ac
=3D 4a=
i>2
� (4a2 +4ac + c2) + c2
+ 4ac
=3D 4a=
i>2
� 4a2 � 4ac � c2 + c=
2
+ 4ac
=3D 0
=3D RHS
(iv) যদি a + b
+ c =3D 0, তেন্ত=
ে দেখুওৱা যে=
সমাধা=
নঃ
দিয়া আছ=
;ে,
a=
+ b + c =3D 0
⇒ =
b
+ c =3D �a
a=
+ b + c =3D 0
⇒ =
c
+ a =3D �b
a=
+ b + c =3D 0
⇒ a + b =3D �c
আমি জা=
;নো যে=
;, যদ=
;ি,
a=
+ b + c =3D 0
তেনেহলে,
a3 + b3 + c3 =3D 3abc
���������������� (1)=
(v) যদি a<=
/span>2 +
b2 + c2 � ab � bc � ca=
=3D 0 তেন্তে=
দú=
3;খুওৱা যে a =3D b =3D c
সমাধা=
নঃ
দিয়া আছ=
;ে,
�a2 =
+ b2
+ c2 � ab � bc � ca =3D 0
⇒ 2(a2 + b2 +=
c2
� ab � bc � ca) =3D 2�0
⇒ 2a2 + 2b2 +=
2c2
� 2ab � 2bc � 2ca =3D 0
⇒ a2 + a2 + <=
i>b2
+ b2 + c2 + c2 � 2=
ab
� 2bc � 2ca =3D 0
⇒ a2 � 2ab + b
⇒ (a � b)2 + (b �=
c)2
+ (c � a)2 =3D 0
⇒ (a � b)2 =3D 0<=
span
lang=3DAS style=3D'font-size:12.0pt;mso-bidi-language:AS'> আৰ=
;ু �=
(b � c)2 =3D 0 <=
span
lang=3DAS style=3D'font-size:12.0pt;mso-bidi-language:AS'>�আৰু �=
(c � a)2 =3D 0
⇒ a � b =3D 0 আৰ=
;ু b � =
c
=3D 0 আৰু c<=
/i> � a =3D 0
⇒ a =3D b আৰ=
;ু b =3D c আৰু c =3D a
⇒ a =3D b =3D c
14. ঘনফল প্ৰক=
2499;তাৰ্থত
নù=
5;ৰ্ণয়
নõ=
3;ৰাকৈ
তø=
2;ৰ
পú=
9;ৰতিটোৰ মান=
b>
নù=
5;ৰ্ণয়
কþ=
4;াঃ �
(i) (� 12)3 +=
(7)
3 + (5) 3
সমাধা=
নঃ
ইয়াত,
�12+7+5 =3D=
0
আমি জা=
;নো যে=
;,
যদি,
a=
+ b + c =3D 0
তেনেহলে,
a3 + b3 + c3 =3D 3abc
গতিকে,
(�12)3=
+(7)3+(5)3
=3D 3�(�12)�7�5
=3D �1260
(ii) (28) 3 +=
(�
15)3 + (� 13)3
সমাধা=
নঃ
ইয়াত,
28 + (�15) =
+ (�13)
=3D 28 �15 �13 =3D 0
আমি জা=
;নো যে=
;,
যদি,
a=
+ b + c =3D 0
তেনেহলে,
a3 + b3 + c3 =3D 3abc
গতিকে,
(28)3<=
/sup>+(�15)3+(�13)3
=3D 3�28(�15)(�13)
=3D 16380
15. তলৰ
দù=
5;য়া
আü=
7;ত
বù=
5;লাকৰ
দù=
6;ঘ
আþ=
4;ু
পú=
9;ৰস্থ
বù=
4;বে
স÷=
8;্ভাব্য ৰাশিবোৰ=
;
উø=
2;িওৱাঃ
(i) =
span>কালিঃ 25a2
� 35a + 12
সমাধা=
নঃ
দিয়া আছ=
;ে কা=
;লি =3D=
25a2 � =
35a
+ 12
এতিয়া,
25a<=
sup>2
� 35a + 12
=3D 25a2 � (15 + 20)a + 12
=3D 25a2 � 15a � 20a =
+ 12
=3D 5a(5a � 3) � =
4(5a
� 3)
=3D (5a<=
/i> � 4)
(5a � 3)
আমি জা=
;নো যে=
;,
আয়তক্ষে=
68;্ৰৰ কালি =3D দৈ=
;ৰ্ঘ্য � প্ৰস্থ
⸫দৈৰ্ঘ্য =3D (5a � 3) আৰু প্ৰস্থ =3D (5a � 4)
(ii) কালিঃ� 35y2 + 13<=
b>y � 12
সমাধা=
নঃ
দিয়া আছ=
;ে কা=
;লি �=3D 35y2 + =
13y
� 12
এতিয়া,
35y<=
sup>2
+ 13y � 12
=3D 35y<=
/i>2
+ (<=
/span>28 � 15)y<=
/i> � 12
=3D 35y<=
/i>2
+ 28y � 15y � 12
=3D 7y=
i> (5y
+ 4) � 3 (5y + 4)
=3D (5y<=
/i> + 4)(7y
� 3)
আমি জা=
;নো যে=
;,
আয়তক্ষে=
68;্ৰ
ফল =3D দৈৰ্=
;ঘ্য � প্=
;ৰস্থ
⸫দৈৰ্ঘ্=
;য =3D =
5y + 4 আৰু প্ৰস=
2509;থ
=3D <=
span
dir=3DLTR>7<=
i>y �
3
16. তলৰ
দù=
5;য়া
ঘ÷=
2;কৰ
মù=
4;ত্ৰা
তù=
5;নিটাৰ
বù=
4;বে
স÷=
8;্ভাব্য ৰাশিকেই=
;টা
কù=
5;
কù=
5;
হ�ব<=
/span>
(i) আয়তন =
=3D 3x2
� 12x
সমাধা=
নঃ
দিয়া আছ=
;ে �আয়তন
=3D 3x2
� 12x
এতিয়া,
3x2
� 12x
=3D 3x(x � 4)
⸫দীঘ � =
প্ৰস্থ � =
উচ্চতা =
=3D 3<=
i>x (x
� 4)
⸫আয়তীয় ঘন=
;কটো দী=
;ঘ =3D 3, প্=
;ৰস্থ�� =3D x আৰু উচ=
;্চতা =3D (<=
span
style=3D'font-size:12.0pt'>x � =
4)
(ii) আয়তন =
=3D 12ky2
+ 8ky � 20k
সমাধা=
নঃ
দিয়া আছ=
;ে আয়=
;তীয়
ঘনকৰ=
span>
আয়তন=
span>
=3D 12ky2
+ 8ky � 20k
এতিয়া,
12ky=
2
+ 8ky � 20k
=3D 4k(3y2=
sup> + 2y
� 5)
=3D 4k{3y2=
sup> +
(5 � 3)y � 5}
=3D 4k(3y2=
sup> + 5y
� 3y � 5)
=3D 4k=
i>{y
(3y + 5) � 1 (3y + 5)}
=3D 4k=
i>(3y
+ 5)(y � 1)
⸫দীঘ � =
প্ৰস্থ � =
উচ্চতা =
=3D 4<=
i>k(3y
+ 5)(y � 1)
⸫আয়তীয় ঘন=
;কটো দী=
;ঘ =3D 4k, প্=
;ৰস্থ�� =3D (3y + 5) আৰ=
;ু উচ=
;্চতা =3D (<=
span
style=3D'font-size:12.0pt;mso-bidi-language:AS'>y � 1)