Select the appropriate values of x that are solutions to f (x)=0, where f (x) = -7x^2 +4x+9

QAmmunity.org

My account
Edit my Profile
Private messages
My favorites

Ask a Question
Questions
Unanswered
Tags
Categories
Ask a Question

asked Sep 20, 2015 230k views

5 votes

Select the appropriate values of x that are solutions to f (x)=0, where f (x) = -7x^2 +4x+9

Mathematics
high-school

Hanseh asked

by Hanseh

7.5k points

0 Comments

Please log in or register to add a comment.

Please log in or register to answer this question.

1 Answer

5 votes

$-7x^2 +4x+9=0\\ \Delta=4^2-4\cdot(-7)\cdot9=16+252=268\\ √(\Delta)=√(268)=2√(67)\\ x_1=(-4-2√(67))/(2\cdot(-7))=(-4-2√(67))/(-14)=(2+√(67))/(7)\approx1.46\\ x_2=(-4+2√(67))/(2\cdot(-7))=(-4+2√(67))/(-14)=(2-√(67))/(7)\approx-0.88\\$