Question

Which of the equations are true identities? a. (3x-2y)(2y-3x)=9x^2-4y^2 b. (2k+5r)(2k-5r)=4k^2-25r^2

Answer 1

option b

Explanation:

Answer 2

b.
`(2k+5r)(2k-5r)`

Explanation:

We have to find the equation which are true identity.

a.
`(3-2y)(2y-3x)`

`(3x-2y)(2y-3x)=3x(2y-3x)-2y(2y-3x)`

`=6xy-9x^2-4y^2+6xy`

`(3-2y)(2y-3x)\\eq 9x^2-4y^2`

b.
`(2k+5r)(2k-5r)`

`(2k)^2-(5r)^2`

Using identity

`(a+b)(a-b)=a^2-b^2`

`4k^2-25r^2`

It is true.

Hence, option b is true.