i need help fining x-intercepts

Question

Find the x-intercepts of the parabola with vertex (1,20) and y-intercept (o,16). Write your answer in this form: (x1,y1),(x2,y2). If necessary, round to the nearest hundredth.

Answer 1

Use vertex form,

y = a(x-1)^2 + 20

Plug in (0, 16),

16 = a + 20
 ==> a = -4

y = -4(x-1)^2 + 20

To find the x-intercept, let y = 0.

0 = -4(x-1)^2 + 20

x = 1 +/- sqrt(5)

Answer: (1 +/- sqrt(5), 0)