# SAT Math: Working Backwards to Find a Quadratic Equation that Models Tennis Ball Height

Anna is playing with a tennis ball, and after 5 seconds she tosses it up in the air. The ball returns to her hand 3 seconds after she tosses it. Assuming the height of the ball is 0 when it is in Anna's hand, which of the following equations models the height of the ball at time t (h(t) ≥ 0)?

Passport to Advanced Math | Radicals and rational exponents |

Product Type | SAT Math |

SAT | SAT Math |

SAT Math | Algebra and Functions Passport to Advanced Math |

Test Prep | SAT Math |

### Transcript

when it is in and his hand which of the

following equations models the height of the ball at time

and he is of age of he is greater than

our legal to zero Okay this kind of ugly isn't

it Alright grab your tennis racket and get ready to

deal with what this problem's serving the problem Asked about

modeling the height of the ball and it can be

assumed that the height is zero when the ball is

in Anna's And yeah we'll just assume that zero It's

in her hand at five seconds and then at three

seconds later I eat eight seconds later So the height

H of tea is zero when t equals five and

T equals eight and we need to make a quadratic

equation in which the following are true That is T

equals five or T minus five zero in T minus

eight zero rights That's quadratic and there's a little parable

a thing in the shape of the ball If you

want to think about it like that well this is

just like finding the X values I either roots of

the zeroes of a quadratic equation but will be working

backwards So H of tea is zero which is ah

quantity T minus five times quantity T minus eight Then

we just multiply everything through So you get T squared

minus thirteen T plus forty That's it So the answer

is a all the wrong answer Choices come from some

weird combination of wrong and attribution sze of eight and

five and negative positive numbers and all that stuff So

that's it It's a in uh say a Fran a 00:01:37.16 --> [endTime] have a ball