Question

Write the factored form of this trinomial 9x^2+18x-7

Answer 1

`(3x+1)(3x-7)`

Explanation:

To write the factored form, multiply a*c from the standard form
`ax^2+bx+c`. Here it is 9*-7 = -63.

Then find factors of -63 that add to b=18.

63: 1, 3, 7, 9, 21, 63

-21 + 3 =18

Split the middle term into -21x + 3x and factor by grouping.

`9x^2-21x+3x-7\\(9x^2-21x)+(3x-7)\\3x(3x-7)+1(3x-7)\\(3x+1)(3x-7)`