First one;
[tex]f(x) = {x}^{2} - 3x - 28[/tex]
As it factorises to:
f(x) = (x - 7)(x + 4)
Which, if set equal to 0, will solve to give the desired solutions like so:
f(x) = (x - 7)(x + 4) = 0
x - 7 = 0 x + 4 = 0
x = 7 x = -4
None of the other quadratics solve to give desired solutions when set equal to 0.
