Question

Explain, in complete sentences, how you would completely factor 15x2 – 25x – 60 by using the grouping method. How would you check your factors for accuracy?

Answer 1

I am hopelessly lost when it comes to factor grouping.

Answer 2

I just read a little bit about it, it still sounds like algeblah.

Answer 3

not sure what you mean by grouping

first thing here is to divide the function by 5:
5 (3x^3 - 5x - 12)

now you need to find two numbers whose product is -12 and where the result of multiply by 3 and adding give the middle number -5

i do this by trial and error

- 3 * 4 = -12
and -3*3 + 4 = -5
so the factors of the expression in the brackets is
(3x + 4)(x - 3) ( + 4x - 9x = -5x)

and final result is

5(3x + 4)(x - 3)

Answer 4

I don't understand what they mean by grouping either. This is the site I was told to read - http://www.mathwarehouse.com/algebra/polynomial/how-to-factor-by-grouping.php

Answer 5

ok - its similar way to mine - i suppose i've got into a groove with these and cant get out of it!
i believe the best way to grasp it is to practice as many as you can

the expressions starting with x^2 are easier than those with ar^2

eg factor x^2 - 2x - 15

- here we need 2 numbers whose product is - 15 and who add up to -2

these are -5 and 3
because -5 * 3 = -15
and -5 + 3 = -2
so factors are
(x - 5)(x + 3)

Answer 6

So it's basically the same thing?

Answer 7

yea

Answer 8

Oh crap, maybe I learned the old way wrong and I was learning this the whole time.

Answer 9

D:

Answer 10

lol

Answer 11

Thanks man.

Answer 12

yw - good luck