SOLUTION: one leg of a right triangle measures three inches less than the other leg. find the length of both legs if the hypotenuse is 4 inches long

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Question 612626: one leg of a right triangle measures three inches less than the other leg. find the length of both legs if the hypotenuse is 4 inches long
Answer by nerdybill(7384) About Me  (Show Source):
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one leg of a right triangle measures three inches less than the other leg. find the length of both legs if the hypotenuse is 4 inches long
.
Let x = longer leg
then
x-3 = shorter leg
.
applying Pythagorean theorem:
x^2 + (x-3)^2 = 4^2
x^2 + (x-3)(x-3) = 16
x^2 + x^2-6x+9 = 16
2x^2-6x+9 = 16
2x^2-6x-7 = 0
applying the "quadratic formula" yields:
x = {3.9, -0.9}
throw out the negative solution (extraneous) leaving
x = 3.9 inches (longer leg)
.
shorter leg:
x-3 = 3.9-3 = .9 inches
.
answer: 3.9 inches and .9 inches
.
.
details of quadratic formula follows:
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 2x%5E2%2B-6x%2B-7+=+0) has the following solutons:

x%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca

For these solutions to exist, the discriminant b%5E2-4ac should not be a negative number.

First, we need to compute the discriminant b%5E2-4ac: b%5E2-4ac=%28-6%29%5E2-4%2A2%2A-7=92.

Discriminant d=92 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28--6%2B-sqrt%28+92+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%28-6%29%2Bsqrt%28+92+%29%29%2F2%5C2+=+3.89791576165636
x%5B2%5D+=+%28-%28-6%29-sqrt%28+92+%29%29%2F2%5C2+=+-0.89791576165636

Quadratic expression 2x%5E2%2B-6x%2B-7 can be factored:
2x%5E2%2B-6x%2B-7+=+2%28x-3.89791576165636%29%2A%28x--0.89791576165636%29
Again, the answer is: 3.89791576165636, -0.89791576165636. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+2%2Ax%5E2%2B-6%2Ax%2B-7+%29