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# factorising quadratics need help! :(

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1. I've been stuck on this fact.quadratic for ages. I know what the real answer is but i can't get there this is the question and method:
factorise 5x^2-17x-12=0
-12x5=-60
-20x3=-60 -20+3=-17
(5x-20)(x+3)=0
x=4 or x=-3

x=4 or x=-3/5 how do i get to -3/5??
2. 5x^2-17x-12=0
5x^2-20x+3x-12=0
5x(x-4)+3(x-4)

(x-4)(5x+3)=0

x-4=0
x=4

5x+3=0
5x=-3
x=/3/5

Hope this helps! Feel free to message me if you still don't understand
-20x3=-60 -20+3=-17
(5x-20)(x+3)=0
This is where you're going wrong, you will need to rewrite the equation as
5x^2-20x+3x-12=0

and then factorise it.
4. (Original post by lizz-ie)
5x^2-17x-12=0
5x^2-20x+3x-12=0
5x(x-4)+3(x-4)

(x-4)(5x+3)=0

x-4=0
x=4

5x+3=0
5x=-3
x=/3/5

Hope this helps! Feel free to message me if you still don't understand
thanks i understand now

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