Homework Help: gr10 math

Posted by Rebecca on Tuesday, May 31, 2011 at 11:08am.

The length of a rectangle is 2cm more than the width. The area is 24cm^2. What are the dimensions of the rectangle?

Let x be the width.
Let x +2 be the the length.
A = lw
24cm^2 = (x+2)x
24cm^2= x^2 + 2x
24cm^2 + x^2 = 2x
25cm^2 = 2x
25cm^2 /2 = 2x /2
12.5cm^2 = x
l = x + 2
l = 12.5 cm^2 + 2
l = 14.5 cm^2
Therefore the dimensions of the rectangle are 12.5cm^2 and 14.5cm^2.
did i do this question right?

gr10 math - PsyDAG, Wednesday, June 1, 2011 at 3:00am
x^2 + 2x = 24

x^2 +2x -24 = 0

Find two factors of -24 that will sum to give the value of the middle term, 2.

(x+6)(x-4) = 0

x = -6 or 4

Since width cannot be a negative number, x = 4, then length = 4 + 2 = 6

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