# mathematics

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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 -

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 -

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)

3x^2+4x-15
= (3x-5)(x+3)

adding 3x^2 + 4x to get 7x^3
that is just unforgivable!

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