You can
put this solution on YOUR website!I'll pick up where you left off (your steps are correct)

Subtract 100 from both sides

Combine like terms
Now let's use the quadratic formula to solve for x:
Starting with the general quadratic
the general solution using the quadratic equation is:
So lets solve

( notice

,

, and

)

Plug in a=2, b=-12, and c=-80

Negate -12 to get 12

Square -12 to get 144 (note: remember when you square -12, you must square the negative as well. This is because

.)

Multiply

to get

Combine like terms in the radicand (everything under the square root)

Simplify the square root (note: If you need help with simplifying the square root, check out this
solver)

Multiply 2 and 2 to get 4
So now the expression breaks down into two parts

or
Lets look at the first part:

Add the terms in the numerator

Divide
So one answer is
Now lets look at the second part:

Subtract the terms in the numerator

Divide
So another answer is
So our possible solutions are:

or
Now lets find each of the leg's lengths:
Leg A:

Plug in x=10

Plug in x=-4
Since a negative length doesn't make sense, the solution x=-4 must be discarded
Leg B:

Plug in x=10

Plug in x=-4
Since a negative length doesn't make sense, the solution x=-4 must be discarded
So the only solution is

where the lengths of the legs are 8 and 6 (or 6 and 8)