SOLUTION: A painting canvas has a length 7 inches longer than its width. If the area is 78 in^2, what are the dimensions of the canvas?

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: A painting canvas has a length 7 inches longer than its width. If the area is 78 in^2, what are the dimensions of the canvas?      Log On


   

Question 154300: A painting canvas has a length 7 inches longer than its width. If the area is 78 in^2, what are the dimensions of the canvas?
Answer by jojo14344(1513) About Me  (Show Source):
You can put this solution on YOUR website!
Remember: A canvas is a rectangular shape,
A=L%2AW
But L=W%2B7
So,
A=%28W%2B7%29%28W%29 ---------------------> working eqn
78=W%5E2%2B7W
W%5E2%2B7W-78=0
Solve by Quadratic: a=1, b=7, & c=-78
x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29
x=%28-7%2B-sqrt%287%5E2-4%2A1%2A-78%29%29%2F%282%2A1%29
x=%28-7%2B-sqrt%2849%2B312%29%29%2F2
x=%28-7%2B-sqrt%28361%29%29%2F2
x=%28-7%2B-19%29%2F2, It has 2 values
x=%28-7%2B19%29%2F2=6inches --------------------> TO BE USED ---> WIDTH
x=%28-7-19%29%2F2=-13 ------------------------> DON'T USED
So, L=W%2B7=6%2B7=13inches
W=6inches
In doubt? Go back working eqn:
78=13%2A6
78in%5E2=78in%5E2
thank you,
Jojo