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Aqa c1 2017

in the c1 2017 aqa paper one of the questions were to factorise
12x^2-59x+72=0

Normally the questions would be alot more simple such as factorise
7x^2-48x+...etc etc..

i usually use a trial and error method but that would take me about an hour to find all the possible combinations, is there a quicker method for this?

Reply 1

Prasiortle

Original post by peanotto

The 12x^2 must come from 12x and x, 6x and 2x, or 4x and 3x. Now in each case you just have to try the possible factor pairs of 72. It should take only a second or two to see whether it gives the required 59x middle term. Alternatively, if you really can't see it, just apply the quadratic formula, making sure you do the arithmetic accurately.