Question

Only need help with part (c)!! thank you!!

Answer 1

Explanation:

`h=(14+5t)(5-t)\\h=70+25t-14t-5t^2\\h=-5t^2+11t+70\\`

a)

`\displaystyle\\a=-5\ \ \ \ \ b=11\ \ \ \ \ \ c=70\\t(h_(max))=(-b)/(2a) \\\\ t(h_(max))=(-11)/(2*(-5)) \\\\t(h_(max))=(-11)/(-10) \\t(h_(max))=1.1 \ seconds`

b)

`h_(max)=-5*1.1^2+11*1.1+70\\\\h_(max)=-6.05+12.1+70\\\\h_(max)=76.05\ m`

c)

`-5t^2+11t+70=72\\-5t^2+11t+70-72=72-72\\-5t^2+11t-2=0`

Hence,

A=11 B=-2

Answer 2

A = 11 , B = - 2

Explanation:

(c)

we are solving the equation

h = (14 + 5t)(5 - t) with h = 72 , that is

(14 + 5t)(5 - t) = 72 ← expand left side using FOIL

70 - 14t + 25t - 5t² = 72 ( subtract 72 from both sides )

- 5t² + 11t - 2 = 0

compare with - 5t² + At + B = 0 , then

A = 11 , B = - 2