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So I got these problems and we didn't go over this in class.

 

What value of x will give the minimum value for 9x^2 + 18x + 7?

 

Help please?

WhichWitchIsWhich  Oct 23, 2017

Best Answer 

 #1
avatar+5237 
+1

The x value that gives the minimum or maximum value for a quadratic function, 

 

ax2 + bx + c  ,  is         - \(\frac{b}{2a}\)    .

 

So for this one...

The x value that gives the minimum or maximum value for

 

9x2 + 18x + 7   is       - \(\frac{18}{2(9)}\)  =  - 1   .

 

And in this case,  9  is positive, so the parabola opens upward, and we have a minimum.

hectictar  Oct 23, 2017
edited by hectictar  Oct 23, 2017
Sort: 

2+0 Answers

 #1
avatar+5237 
+1
Best Answer

The x value that gives the minimum or maximum value for a quadratic function, 

 

ax2 + bx + c  ,  is         - \(\frac{b}{2a}\)    .

 

So for this one...

The x value that gives the minimum or maximum value for

 

9x2 + 18x + 7   is       - \(\frac{18}{2(9)}\)  =  - 1   .

 

And in this case,  9  is positive, so the parabola opens upward, and we have a minimum.

hectictar  Oct 23, 2017
edited by hectictar  Oct 23, 2017
 #2
avatar+272 
+1

:D  👍

WhichWitchIsWhich  Oct 23, 2017

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