Question

Which equation is true?

9x2 – 25 = (3x – 5)(3x – 5)
9x2 – 25 = (3x – 5)(3x + 5)
9x2 – 25 = –(3x + 5)(3x + 5)
9x2 – 25 = –(3x + 5)(3x – 5)

Answer 1

Hello,

Answer B


But this is not an equation!!!!! (only an expression)

Answer 2

Answer :
`9x^2 - 25 = (3x - 5)(3x + 5)`

(1)
`9x^2 - 25 = (3x - 5)(3x - 5)`

Use FOIL method to mulitply (3x – 5)(3x – 5)

`(3x - 5)(3x - 5) = 9x^2 - 30x + 25`

(2)
`9x^2 - 25 = (3x - 5)(3x + 5)`

Use FOIL method to mulitply (3x - 5)(3x + 5)

`(3x - 5)(3x - 5) = 9x^2 - 15x + 15x - 25 = 9x^2 - 25`

(3)
`9x^2 - 25 = -(3x + 5)(3x + 5)`

Use FOIL method to mulitply -(3x + 5)(3x + 5)

`-(3x + 5)(3x + 5) = -(9x^2 + 30x + 25) = -9x^2 -30x -25`

(4)
`9x^2 - 25 = -(3x + 5)(3x - 5)`

Use FOIL method to mulitply -(3x + 5)(3x - 5)

`-(3x + 5)(3x - 5) = -(9x^2 - 25) = -9x^2 + 25`

So equation 2 is true