Question 78608
The formula for the area of a rectangle is A = L*W in which A represents the Area, L is the
Length and W is the width.
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The problem states that the Area is given by {{{x^2 + 50x}}} and the Width is {{{x}}}.
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Substitute these two values into the area formula and you get:
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{{{x^2 + 50x = L*x}}}
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To solve for L, divide both sides of this equation by x, the multiplier of L and you get:
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{{{(x^2 + 50x)/x = L}}}
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Divide the x of the denominator into each of the two terms in the parentheses and the
result is:
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{{{x^2/x + 50x/x = L}}}
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recall that {{{x^2 = x*x}}} so dividing x^2 by x is the same as {{{x*x/x}}} and the x
in the denominator cancels with one of the x's in the numerator.  So the result is of
this division is just x.  Similarly, when you divide {{{50x}}} by {{{x}}} the x in the 
denominator cancels the x in the numerator.  Therefore, this division just results in
50.  So when these divisions are performed the equation simplifies to:
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{{{x + 50 = L}}}
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and this is the binomial you were asked to find:
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{{{L = x + 50}}}
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and when you solve for L, don't forget that the answer is in centimeters.
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Hope this helps you to understand the problem a little better.