Show that $x^4-8x^2+(1-m)x+1-c=(x-a)^2(x-b)^2$

functions tangent-line

Hints

$f(x)-g(x)=0$ has repeated roots at $x=a$ and $x=b$, then comparing coefficients (don't miss the $x^3$ term).

See also another post here.

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