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.

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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

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