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Square roots and common factors
Find both roots by taking square roots or taking out a common factor.
Example 1
x2=81
Show worked answer
Answer: x=9x=−9
- Take both square roots of 81:x=±9.
- Both 9 and −9 square to 81.
- Therefore x=9 or x=−9.
- Enter both roots, in either order.
Example 2
4x2=324
Show worked answer
Answer: x=9x=−9
- Divide both sides by 4:x2=81.
- Taking both square roots gives x=±9.
- Therefore x=9 or x=−9.
- Enter both roots, in either order.
Example 3
x2−81=0
Show worked answer
Answer: x=9x=−9
- Add 81 to both sides: x2=81.
- Take both square roots, not only the positive one: x=±9.
- Therefore x=9 or x=−9.
- Enter both roots, in either order.
Put it into practice.
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