Answer:
x = 100
Step-by-step explanation:
The larger area is ...
A = LW
A = (300+x)(200+x) = x^2 +500x +60,000
The smaller area is ...
A = (200)(300) = 60,000
We want the larger area to be double the smaller area, so ...
x^2 +500x +60,000 = 2(60,000)
x^2 +500x = 60,000 . . . . . . . . . . . . subtract 60,000
x^2 +500x + 62500 = 122500 . . . add 250^2 to complete the square
(x +250)^2 = 350^2
We're interested in the positive solution, so we can take the positive square root to find it:
x +250 = 350
x = 100 . . . . . . . . . subtract 250
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The graph shows the quadratic in the form x^2 +500x -60,000. That is, we're looking for zeros (x-intercepts) of the function.
