Posted by **STACEY** on Saturday, June 13, 2009 at 8:16pm.

Factorise copletely

1) 2ax+3ay-2bx-3by

2)5x^2-20

3)3x^2+4x-15 is the ans to this one = 7x^3-15

- mathematics -
**Damon**, Saturday, June 13, 2009 at 8:33pm
You mean factor

a(2x+3y)-b(2x+3y)

= (a-b)(2x+3y)

5(x^2-4)

= 5 (x-2)(x+2)

(3x-5)(x+3)

- mathematics -
**Reiny**, Saturday, June 13, 2009 at 8:34pm
first one is "grouping"

2ax+3ay-2bx-3by

= a(2x+3y) - b(2x+3y)

= (2x+3y)(a-b)

second, common factor then difference of squares

5x^2-20

= 5(x^2 - 4)

= 5(x+2)(x-2)

third, general quadratic

3x^2+4x-15

= (3x-5)(x+3)

looks like you got your answer by

adding 3x^2 + 4x to get 7x^3

that is just unforgivable!

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