x²+8x-9

x²+8x-9

Answers
What is it you want to know?
jon.ellis
05 April 2011
are you trying to factorise?
chloe
05 April 2011
if you are then we know this is a quadratic equation because of the formation ax^2 + bx + c so we know that it's going to have to go into the form (x+a) (x+b)
chloe
05 April 2011
Factors of -9 are 9 and -1 or -9 and 1 or -3 and 3
chloe
05 April 2011
So, in order to find out what a and b are, we have to ask ourselves what factors of -9 add up to make 8
chloe
05 April 2011
so we get (x+9) (x-1)
chloe
05 April 2011
so we choose these two to put in our brackets for a and b
chloe
05 April 2011
Out of those pairs of numbers the ones that add up to 8 are 9 and -1
chloe
05 April 2011
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