A grasshopper jumps off a tree stump. The height, in feet, of the grasshopper above the ground after t seconds is modeled by the function shown below. After how many seconds will the grasshopper land on the ground? Round to the nearest tenth.

h(t) = -t^2 + 4/3t + 1/4

A. -0.2 seconds
B. 0.5 seconds
C. 1.5 seconds
D. 0.7 seconds

Respuesta :

Riia

The height, in feet, of the grasshopper above the ground after t seconds is modeled by the function , which is

[tex] h(t) =-t^2+\frac{4}{3}t+ \frac{1}{4} [/tex]

When the grasshopper land on the ground,

[tex] h(t)=0 [/tex]

that is,

[tex] -t^2+\frac{4}{3}t+ \frac{1}{4}=0 [/tex]

Multiplying whole equation by 12 to get rid of denominators 3 and 4

[tex] -12t^2+16t +3=0 [/tex]

[tex] (3-2t)(6t+1)=0
\\
3-2t=0 , 6t+1=0
\\
t= \frac{3}{2} , \frac{-1}{6} [/tex]

And time cant be negative, so the correct option is

[tex] t = \frac{3}{2}=1.5 seconds [/tex]

Correct option is C .