Worked examples
Two examples
Example 1
Solve: x2 = 49
- Take the square root of both sides.
- There are two answers: 7 × 7 = 49, and (−7) × (−7) = 49 too.
Answer: x = 7 or x = −7
Example 2
Solve: 2x2 = 72
- Divide both sides by 2: x2 = 36.
- Take the square root: two answers.
Answer: x = 6 or x = −6
Where this is taught: Quiz 40: Quadratic Equations, “Two shortcuts worth having”
The drill
Ten problems
How many:
Type both answers with a comma between them, like 7, -7. Then press Check my answers at the bottom.Write the numbers on the line. The answer key, with the reasoning, is on the last page.