# TSI Math: Finding a Line's x-Intercept Given a Point on that Line

Which of the following points is a location where the function f(x) = -2x² + 12x + 54 crosses the horizontal axis?

Intermediate Algebra and Functions | Quadratic and Other Polynomial Expressions, Equations, and Functions |

Mathematics and Statistics Assessment | Quadratic and Other Polynomial Expressions, and Functions |

Product Type | TSI |

TSI | Mathematics and Statistics Assessment TSI Math TSI Mathematics |

TSI Math | Intermediate Algebra and Functions |

TSI Mathematics | Intermediate Algebra and Functions |

Test Prep | TSI |

### Transcript

Who knows The chicken Probably doesn't It just does what

it wants A good thing We do know why the

function crossed the horizontal axis It was equal to zero

c that's the horizontal axis there That ex thing we

want to find the values of x that make f

of x equals zero So we need to solve the

if equation zero equals negative to x squared plus twelve

ax plus fifty for so basically a factoring question We

feel queasy when the coefficient of x squared isn't equal

toe one So the first step is to factor out

negative two from the right side of the equation Then

we got zero equals negative two times quantity x squared

among six x there minus twenty seven Right now we

gotta factor the quadratic inside the parentheses We got two

factors of negative twenty seven So what are they What

times What is twenty seventy s One in twenty seven

Morning Look in the back row There What else Times

What is twenty seven Yeah nine and three nine times

Three is twenty seven and we know that we've got

to get a negative six year so we're going to

do the negative sign on the nine and the positive

sign on the three because negative nine and three is

that negative six So that works on the negative six

x thingy there and we gotta minus twenty seven We

all play that negative nine times three so that's what

it looks like we got zero equals negative two times

princess expose three and princes x minus nine right there

so we find a solution by setting the expressions inside

The princess is equal to zero in solving for acts

Well first if x plus three zero than x has

to be negative three and second of x minus nine

to zero the next has to be nine We'll fx

then crosses the horizontal axis at the point Negative three

zero and nine zero that's it So the answer is 00:01:58.455 --> [endTime] d we're done