x(x + 6) > 16 - 7x + 20
x^2 + 6x + 7x - 36 > 0
x^2 + 13x - 36 > 0
x^2 + 13x > 36 complete the square on x
x^2 + 13x + 169/4 > 36 + 169/4
( x + 13/2)^2 > 313/4
x + 13/2 > sqrt (313) / 2 x + 13/2 < -sqrt(313)/2
x > [ sqrt (313) - 13 ] / 2 x < [ -sqrt (313) - 13 ] / 2
Solution
(-inf , [ -sqrt (313) -13 ] / 2 ) U ( [sqrt (313 - 13 ] / 2 , inf )