Because f(x)=x^2 is the parent function of a quadratic, it has one x-intercept at (0,0), no shifts up or down. But because g(x)=(x+2)^2-7 is a quadratic being shifted 2 units to the left and most importantly 7 units down, the function will cross the x-intercept 2 times.
I hope this is the answer you were looking for!
