Can someone me with this and show how they did it?

Now, a double root, or a root with a multiplicity of 2, means the root is there twice, namely, for a quadratic, that has a root of say "a", like x² + bx + c, the roots will be 0 = (x + a)(x + a), which produces a root of "a" twice, or a zero with a multiplicity of 2.

so. hmmmm let's use that, keeping in mind that, in the trinomial, the  middle term, as you know from factoring, is ax + ax, or 2ax.  The constant or last term is just the product of a * a, or a², thus