SOLUTION: A rectangle measures 4 ft by 10 ft. We’d like to double the area by extending each side by the same amount. How much do we need to extend each side? Find the answer by writing

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: A rectangle measures 4 ft by 10 ft. We’d like to double the area by extending each side by the same amount. How much do we need to extend each side? Find the answer by writing      Log On


   

Question 1185597: A rectangle measures 4 ft by 10 ft. We’d like to double the area by extending each side by the same amount. How much do we need to extend each side? Find the answer by writing and solving a quadratic equation.
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
From 4%2A10 ft%5E2 to %284%2Bx%29%2810%2Bx%29=2%2A4%2A10

4%2A10%2B10x%2B4x%2Bx%5E2=2%2A4%2A10
14x%2Bx%5E2=4%2A10
x%5E2%2B14x=40
x%5E2%2B14x-40=0
x=%28-14%2B-+sqrt%28196%2B4%2A40%29%29%2F2
x=%28-14%2B-+sqrt%28356%29%29%2F2
x=-7%2Bsqrt%2889%29 about2.434

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check: %284%2B2.434%29%2810%2B2.434%29=6.434%2A12.434=80.00