Worked examples
Two examples
Example 1
Solve: x2 + 5x + 6 = 0
- Two numbers that multiply to 6 and add to 5: 2 and 3. So (x + 2)(x + 3) = 0.
- A product is 0 only when a factor is 0: x + 2 = 0 or x + 3 = 0.
Answer: x = −2 or x = −3
Example 2
Solve: x2 − x − 12 = 0
- Two numbers that multiply to −12 and add to −1: −4 and 3. So (x − 4)(x + 3) = 0.
Answer: x = 4 or x = −3
Where this is taught: Quiz 40: Quadratic Equations, “Solving by factoring”
The drill
Ten problems
This drill also has challenge problems. They use the same skill, set up the way the GED test sometimes sets up a problem, so that it looks new at first.
How many:
Type both answers with a comma between them, like -2, 3. 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.