If f(x)=x^2 +2x -1
a) 2=x^2+2x-1
0=x^2+2x-3
0=(x+3)(x-1) x=-3 or 1
b) 14=x^2+2x-1
0=x^2+2x-15
0=(x+5)(x-3) x=-5 or 3
c) 7=x^2+2x-1
0=x^2+2x-8
0=(x+4)(x-2) x=-4 or 2
d) -1=x^2+2x-1
0=x^2+2x+0
0=(x+2)x x=0 or -2
Since this function involves a quadratic equation, there are technically two possible inputs that will give you the same output. In your case, you just have to match one of the possible inputs to its output (the numbers on the left originally given, from what it seems.) Hope this helps