SOLUTION: If x�y=7 and xy=6 then find the value of x^4+1/x^4

Question 889919: If x�y=7 and xy=6 then find the value of x^4+1/x^4
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
If x�y=7 and xy=6 then find the value of x^4+1/x^4
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x�y=7 --> y = x-7
xy=6
x*(x-7) = 6
x^2 - 7x - 6 = 0

Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=73 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 7.77200187265877, -0.772001872658765. Here's your graph:

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