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WHAT TO DO:
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HOW TO DO IT: |
| Example: 6x2 + 23x + 20 |
6x2 + 23x + 20 |
| Multiply 6· 20:
|
GN
6·20 = 120 |
| Find pairs of integer factors
(largest first)
|
 |
| Sign before last term is +
so find pair with the SUM of 23
|
15 + 8 = 23 |
| Both have same sign as middle number + 23
|
+15, + 8 |
| Rewrite polynomial 6x2 + 23x + 20 with 4 terms having correct signs:
|
6x2 + 15x + 8x + 20 |
| Group terms 2 by 2 |
6x2 + 15x + 8x + 20 |
| Factor common term from each group: |
3x(2x + 5) + 4(2x + 5) |
| Note that (2x + 5) is now common factor
and factor it out to get:
|
(3x + 4)(2x + 5) |
| Multiply by FOIL to check:
Check:
Always Check: |
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