SOLUTION: the length of a rectangle is 8cm greater than twice its width.find the dimensions if the area is 42cm square

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Question 422141: the length of a rectangle is 8cm greater than twice its width.find the dimensions if the area is 42cm square
Answer by emargo19(101) About Me  (Show Source):
You can put this solution on YOUR website!
Let the width be x
Let the length be 2x+8
x(2x+8)=42
2x^2+8x=42
2x^2+8x-42=0
Lets use the quadratic equation to factor the equation
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a=2 b=8 c=-42
x+=+%28-8+%2B-+sqrt%28+8%5E2-4%2A2%2A-42+%29%29%2F%282%2A2%29+
x+=+%28-8+%2B-+sqrt%2864%2B336%29%29%2F4+
x+=+%28-8+%2B-+sqrt%28400%29%29%2F4+
x+=+%28-8+%2B+20%29%2F%284%29+ x+=+%28-8+-20%29%2F%284%29+
x+=+%2812%29%2F%284%29+ x+=+%28-28%29%2F%284%29+
x+=+3+ x+=+-7+