SOLUTION: the length of a rectangle is 5 cm more than 3 times the width. The area is 42cm^2. Find the dimensions.

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Question 523729: the length of a rectangle is 5 cm more than 3 times the width. The area is 42cm^2. Find the dimensions.
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
width be x
length = 3x+5
Area = L*W
Area = x(3x+5)
3x^2+5x=42
3x^2+5x-42=0
a= 3 ,b= 5 ,c= -42

b^2-4ac= 25 + 504
b^2-4ac= 529
x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=%28-12%2B21%29%2F%2812%29
x1=( -5 + 23 )/ 6
x1= 3
x2=( -5 -23 ) / 6
x2= -4.67
ignore negative value
width = 3 cm
length =>3x+5=>3*3+5= 14 cm