Answer:
[tex](3x+1)(3x-7)[/tex]
Step-by-step explanation:
To write the factored form, multiply a*c from the standard form [tex]ax^2+bx+c[/tex]. 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.
[tex]9x^2-21x+3x-7\\(9x^2-21x)+(3x-7)\\3x(3x-7)+1(3x-7)\\(3x+1)(3x-7)[/tex]
