Hi i have an exam in the comming days and i need help factoring quadratics with the box method
2y^2-y-15
Can anyone factor this and explain? thanks!
$\displaystyle 2y^2 - y - 15$
We have a=2; b=-1; c=-15;
Which means ac=-30;
Find factors of -30 that add up to -1;
In this case, 5 and -6;
Then, draw your box:
| 2y^2 ....| ******|
| ********| -15 **|
Add the numbers you found as y multipliers;
| 2y^2 | 5y |
| -6y...| -15 |
Then, find the common factors of each row and column to get;
............2y........+5........
y....... | 2y2^2 | 5y |
-3.......| -6y.....| -15|
You now have the following (y-3)(2y+5);
Try it yourself to see if it works.