# how do i figure out x2+7x+10=0

how do i figure out x2+7x+10=0

Do you recognise the quadratic forumla?
theo.cushion
13 April 2012
The other handy method if you don't recognise the quadratic formula is to try and factorise the equation . By factorize I mean split it into the form where when you multiply out the brackets you get the above equation. Let me konw if you need a hand moving on from this bit.
sinsua
14 April 2012
it doesnt matter which way around so you then know that x+2=0 and x+5=0
fiaraz
25 April 2012
oh dear... those are terribly horrible looking ways, their is an easier way. Whe you see a problem that looks like that ask your self two questions. What two number times together to give you 10 and add together to give you 7? OK have you thought about it? teh answer is 5 and 2 so what you do is write your answer like this (x+2)(x+5) = 0
fiaraz
25 April 2012
doing this to both equations givex x=-2 and x=-5!!!
fiaraz
25 April 2012
I am using separate posts so you can see each step. ok so now i rearrange each equation so if i take x+2=0 then depending on how you have been taught you either take two away from both sides or move the +2 over to give you -2
fiaraz
25 April 2012
you take the number infront of x2 which is 1 and times it t othe last number which is 10
tishax2
25 April 2012
what times together to give 10 and adds together to give 7 ? 5 and 2 ? then do x2+5x+2x=10 then factorise which will end up as (x+2) and (x+5) and x will either equal -2 or -5
tishax2
25 April 2012
right but wouldn't introduce the coefficient of X2 until a student is comfortable and has become proficient at factorizing, but hey thats me!
fiaraz
25 April 2012
the number infront of the the 'x2' is timesd by the single number at the end then you need to find what times together to get that number and also add together to give you the number infront of the single 'x' when you figured that out, you factorise the fiirst section putting some into brackets and some out side, you do the same with the second section you will NEED to end up having two brackets with the same things inside it along with something else on the outside infront of it whatever is in front the bracket is put into a seperate bracket the answer will be the newly made bracket and one of the brackets that had a 'twin' dividing etc will give you the value of x
tishax2
25 April 2012
x2+7x+10=0 ? [5 and 2, times to give 10 and add to give 7] [substitue]x2+5x+2x+10 [factorise] x(x+5)+2(x+5) [create seperate brackets] (x+2)(x+5) [find what x is for each] x=-2or-5
tishax2
25 April 2012