- #1
RJLiberator
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Homework Statement
Find all real numbers k such that x^2+kx+k is reducible in ℝ[x].
Homework Equations
The Attempt at a Solution
This seems like it is simple, but it is new to me so I am looking for confirmation.
We know we can find the roots of a polynomial with b^2-4ab. We want b^2-4ab to be greater than 0 for it to have roots.
But we note:
Here, a = 1, b = b, c = b.
When we have b^2-4*b = 0 we get the answers either b = 0 or b = 4.
Both of these are solutions to the problem question.
If we let b(b-4) > 0 then we get a whole array of numbers that are not solutions to this problem.
So I am stating that b =0 and b = 4 are the only solutions to the problem as they are the only solutions to b^2-4ab = 0. But why is this so?