We are struggling with this part

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y = 5000x - 625x^2
First find dy/dx = 5000-1250x

Now there are turning points when dy/dx = 0, so:

0 = 5000 - 1250x
1250x = 5000
x = 500/125 or 4

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We see that you have divided both sides by x, but should it not then be

5000-625x ??


Thanks

leigh