The length of a side of a rectangle is 2 units less than a number, and the width is 4 units more than the length. Which of the following expressions represents the area of the rectangle, in square units?

Question

A. x^2+2x+4
B. x^2-2x+8
C. x^2-4
D. x^2+4

Answer 1

x = a number

L = x - 2

W = L + 4 = x - 2 + 4 = x + 2

A = L * W =

( x - 2 ) * ( x + 2 ) =

x ^ 2 - 2 ^ 2 =

x ^ 2 - 4

Answer C

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Remark:

( a - b ) ( a + b ) = a ^ 2 - b ^ 2
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