For the quadratics at this level, every one is the same three moves: get the x² by itself, square-root both sides, and remember the ±. No fancy formula needed.
The Three Moves
One — get x² on its own. If it already reads x² = 36, you're set. If it's x² − 36 = 0, add 36 to both sides (just like a linear equation) to get x² = 36 first.
Two — square-root both sides. The square root undoes the square: x = ±√36.
Three — write both signs. √36 = 6, so x = 6 or x = −6. The ± is not optional — more on why next rung.
A Worked One
Solve x² − 49 = 0. Add 49: x² = 49. Square-root: x = ±√49. And √49 = 7, so x = 7 or x = −7. Done.
Keep the Numbers Friendly
At this stage the right-hand side is a perfect square — 4, 9, 16, 25, 36… — so the root is a whole number you can often spot. If you can't recall it, the times-tables get you there: "7 times 7 is 49, so √49 = 7." Squaring built it; square-rooting takes it apart.