The real numbers $x$ and $y$ are such that \begin{align*} x + y &= 4, \\ x^2 + y^2 &= 22, \\ x^4 &= y^4 - 176 \sqrt{
7}. \end{align*}Compute $x - y.$
2 answers:
Answer:
-2sqrt(7)
Step-by-step explanation:
Solution:
From the third equation, $x^4 - y^4 = -176 \sqrt{7}.$
By difference of squares, we can write
\[x^4 - y^4 = (x^2 + y^2)(x^2 - y^2) = (x^2 + y^2)(x + y)(x - y).\]Then $-176 \sqrt{7} = (22)(4)(x - y),$ so $x - y = \boxed{-2 \sqrt{7}}.$
You get everything you need from factoring the last expression:

The left side is a difference of squares, and we get another difference of squares upon factoring. We end up with

Plug in everything you know and solve for
:

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