Quadratic Grade 10 math question!?

Question

h=-5t2 +30t +10

the 2 is the squared

When will the h be zero?

h=height

t=time

please dont just give answer show steps!

Answer 1

When will the h be zero?

Set the h as 0

0 = -5t^2 +30t + 10

move it to the other side

5t^2-30t-10 = 0

5(t^2-6t-2)=0

t^2-6t-2=0

t = [6±√(-6)^2-4(1)(-2) ]/ 2

t = [6±√44 ]/ 2

t = [6±2√11]/2

t = 3±√11

You should discard 3-√11 because there is no such thing as negative time