A. (1.20,-0.65)

B. (-9,5)

C. (-0.56,-0.78)

D. (-1.29,0.71)

Select the approximate values of x that are solutions to f(x)=0, where f(x)=-9x^2+5x+7

A. (1.20,-0.65)

B. (-9,5)

C. (-0.56,-0.78)

D. (-1.29,0.71)

A. (1.20,-0.65)

B. (-9,5)

C. (-0.56,-0.78)

D. (-1.29,0.71)

I believe the answer is D. This is not my final I have two weeks to cram for the test and need to refresh on topics earlier in the course. My math Partner came up with a different answer and we do not know who is correct or if we skipped a step.

Tutors, sign in to answer this question.

Krystal S. | The Math Magician The Math Magician

You should use the quadratic formula to solve this problem.

If f(x) = ax^{2} + bx + c = 0 then x = [-b +- sqrt(b^{2} - 4ac)]/2a

So we have -9x^2+5x+7 = 0. We just substitute in to our equation

x = [-5 + sqrt{5^{2 }- 4(-9)(7)}/[2(-9)] and x = [-5 - sqrt{5^{2} - 4(-9)(7)}/[2(-9)]

x = [-5 + sqrt{25 +252]/-18 and x = [-5 - sqrt{25 +252]/-18

x = [-5 + sqrt{277}]/-18 and x = [-5 - sqrt{277}]/-18

x ~ . 65 and x ~ 1.20

A

Already have an account? Log in

By signing up, I agree to Wyzant’s terms of use and privacy policy.

Or

To present the tutors that are the best fit for you, we’ll need your ZIP code.

Your Facebook email address is associated with a Wyzant tutor account. Please use a different email address to create a new student account.

Good news! It looks like you already have an account registered with the email address **you provided**.

It looks like this is your first time here. Welcome!

To present the tutors that are the best fit for you, we’ll need your ZIP code.

Please try again, our system had a problem processing your request.

Devin M.

Experienced and Enthusiastic Math Tutor!

$8.75 per 15 min

View Profile >

Randy P.

Discover the mysteries of the world of Math And Physics

$8.75 per 15 min

View Profile >

John A.

STEM Aggie Tutor specializing in Logic tutoring (TAMU/Blinn)

$8.75 per 15 min

View Profile >

## Comments