You may want to review solving quadratic equations first.

Quadratic functions can also appear in the form *y* =
−4 ⁄ 7 * (*x* + 2)^{2} +
1 ⁄ 5. Now, to find the *y*-intercept,
just plug in 0 for *x*. (The answer will be
−73 ⁄ 35.) To find the vertex is now
very easy; it's just −2. In general, just take whatever's
added to *x* and take the additive inverse of it (so if it
had been *x* − 2 then it would be 2).

The roles of *x* and *y* can be reversed. In that case,
to find the *x*-intercept, you plug in 0 for *y*.