SOLUTION: the width of a rectangle is 15 cm less than 3 times the lenght if the area is 42 square cm find the dimensions of the rectangle

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Question 1063328: the width of a rectangle is 15 cm less than 3 times the lenght if the area is 42 square cm find the dimensions of the rectangle
Answer by ikleyn(52794) About Me  (Show Source):
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the width of a rectangle is 15 cm less than 3 times the lenght if the area is 42 square cm find the dimensions of the rectangle
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LW = 42,     (1)    ("the area is 42 square cm")
W = 3L-15.   (2)    ("the width of a rectangle is 15 cm less than 3 times the lenght")

Substitute expression for W from (2) into the equation (1) replacing W. You will get

L*(3L - 15) = 42.

Simplify and solve for L this quadratic equation.