Algebra | Integers or fractions

Question

Suppose that f(x)=x^2+11x+18.

Find the values of x such that f(x)=8.

Find the values of x such f(x)=30.

What points are on the graph of f?

Answer 1

x^2 + 11x + 18 = 8

x^2 + 11x + 10 = 0

(x+10)(x+1) = 0

x = -1 or -10 if f(x) = 8

x^2 + 11x + 18 = 30

x^2 + 11x - 12 = 0

(x+12)(x-1) = 0

x = 1 or -12 if f(x) =30

f(x) = x^2+ 11x + 18 = (x+9)(x+2) where x=-2 and -9 are roots or zeroes (-2,0) and (-9,0) are points on the graph of f(x), where the parabola intersects the x axis