SOLUTION: the length of a rectangle is is 10m less than twise the width..what are dimension s of this rectangle if the area is 72m^2

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Question 401529: the length of a rectangle is is 10m less than twise the width..what are dimension s of this rectangle if the area is 72m^2
Answer by Tatiana_Stebko(1539) About Me  (Show Source):
You can put this solution on YOUR website!
Let x is the width of a rectangle,
The length of a rectangle is 10m less than twice the width, so the lenght is %282x-10%29 m
The area of rectangle is x%2A%282x-10%29, from text the area is 72m^2
equation
x%2A%282x-10%29=72
2x%5E2-10x=72
2x%5E2-10x-72=0 divide both sides by 2
x%5E2-5x-36=0 quadratic equation
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
x+=+%28-%28-5%29+%2B-+sqrt%28+%28-5%29%5E2-4%2A1%2A%28-36%29%29%29%2F%282%2A1%29+
x+=+%285+%2B+sqrt%28+169%29%29%2F2+ or x+=+%285-+sqrt%28+169%29%29%2F2+
x+=+%285+%2B+13%29%2F2+ or x+=+%285-+13%29%2F2+
x+=+18%2F2+ or x+=+-+8%2F2+
x+=9+ or x+=+-+4+<0,extraneous root of the equation does not satisfy the conditions of the problem
So width of a rectangle is 9 m, the length of a rectangle is %282x-10%29=%282%2A9-10%29=8m
Answer 9 m and 8 m