If x^(2) -y^(2) =21, then 2(x+y)(x-y)= A. 21/2 B. 18 C. 21 D. 42 Please explain.

Question

If
`x^(2) -y^(2) =21`, then
`2(x+y)(x-y)=`

A. 21/2
B. 18
C. 21
D. 42
Please explain.

Answer 1

Answer is D 42

`x^(2) - y^(2) =(x+y)(x-y)`
It is given
=21
Multiply both side by 2
U will bet 21×2=42