Question

Expand each of the following cubes using suitable identities:

1) (2x - 1)³

2) (5 - b)³

3) (x - 2y)³ ​

Answer 1

Step-by-step explanation:

(i) (2x+1)  

3

=(2x)  

3

+(1)  

3

−3(2x)(1)(2x+1)

           =8x  

3

+1+6x(2x+1)=8x  

3

+12x  

2

+6x+1

(ii) (2a−3b)  

3

=(2a)  

3

−(3b)  

3

+3(2a)(3b)(2a−3b)

=8a  

3

+27b  

3

−18ab(2a−3b)=8a  

3

−27b  

3

−36a  

2

b+54ab  

2

 

(iii) (  

2

3

​

x+1)  

3

=(  

2

3

​

)x  

3

+(1)  

3

+3(  

2

3

​

x)(1)(  

2

3

​

x+1)

=  

8

27

​

x  

3

+1+  

2

9

​

(  

2

3

​

+1)=  

8

27

​

x  

3

+  

4

27

​

x  

2

+  

2

9

​

x+1

(iv) [x−  

3

2

​

y]  

3

=  x  

3

−3×x  

2

×  

3

2

​

y+3×x×(  

3

2

​

y)  

2

+(  

3

2

​

y)  

3

 

                         =x  

3

−2x  

2

y+  

3

4

​

xy  

2

+  

27

8

​

y  

hope you understood

Answer 2

Answer:

here is your answer dear

Step-by-step explanation:

hope it helps u..pls mark me as BRAINLIEST :)