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What is the maximum value of the expression -5r^2 + 40r - 12 for real r?

 Jul 31, 2019
 #1
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Use the quadratic formula to solve for r. Then sub both values of r into your equation and see which one gives a higher value.

 Jul 31, 2019
 #2
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This is a dome shaped parabola (due to the negative coefficient of the x^2 term)

the r value at the max point will be given by    -b /2a         where a =-5     b = 40     sooooooo   r = ?

 

Once you FIND this r value, sub in to the equation to find the max value of the expression....   You CAN do it ! 

 Jul 31, 2019

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