Answer: x^2 - 25 (choice C)
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Step-by-step explanation:
Let's say we replace the "x+5" with some other letter. Let's use L for length.
We'll keep the width x-5 the same.
area = length*width
area = L*(x-5)
area = L*x + L*(-5)
area = xL - 5L
At this point, we would then plug in L = x+5 and distribute like so:
area = x( L ) - 5( L )
area = x( x+5 ) - 5( x+5 )
area = x^2 + 5x - 5x - 25
area = x^2 - 25
Side note: (x+5)(x-5) = x^2 - 25 is an application of the difference of squares rule.