What is the value of k for which (k^2 - 5k + 4)x^2 + (k^2 - 3k - 4)x + (k^2 - 4k) = 0 is an identity ?

Explanation

For an equation to be an identity for all x, all its coefficients must be zero. Solving k^2-5k+4=0, k^2-3k-4=0, and k^2-4k=0 yields a common value of k=4.

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