When there are 22 apple trees per acre, the average yield has been found to be 700 apples per tree. for each additional tree planted per acre, the yield per tree decreases by 12 apples per tree. how many additional trees per acre should be planted to maximize the yield? (round your answer to the nearest whole number.)

To solve this, 
Let apple trees = x 
and let yield per tree = 700 - 12x 

trees * yield per tree = total yield 
let total yield = y 

(22 + x) * (700 -15x) = y 
trees x apples= yield 
22 x 700 = 11,000 
23 x 688 = 11, 155 
24 x 673 = 11,280 
25 x 664 = 11,375 
26 x 652 = 11,440 
27 x 640 = 11,475 
28 x 628 = 11,480 
29 x 616 = 11,455

So the correct answer is 29 trees per acre should be planted to maximize the yield. 

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The answer is part a: use