1: `x`-intercepts are where there are real solutions.

4: The discriminant is `b`^{2} – 4`ac`, and it is either positive, zero, or negative.

7: Get the square by itself, and then take the square root on each side.

8: This is like the previous problem, except there are two steps (addition and division) needed before taking the square root on each side.

13: You can use the quadratic formula if you set the equation equal to zero first. Make sure that `b`^{2} turns out positive, even though `b` will be negative.

25: A zero is a value that makes the expression equal to zero.

30: Pick two numbers `a` and `c` such that (-8)^{2} – 4`ac` is greater than zero.

38: An `x`-intercept represents a real zero.

43: You can substitute 16 – 4`y` for `x` in the second equation.

46: The axis of symmetry is `x` ＝ `h`, where `h` ＝ -`b` ÷ 2`a`.