Thread: Factorising + Quadratics

Can anyone show me the way to solve this following equation by factorising, i need to see all workin out so i can fully understand, i've been pulling my hair out all day today. hope someone can help me.


2xsquared -5x - 7 = 0

Many Thanks
Chris

read this post:
http://www.mathhelpforum.com/math-he...ctorising.html

Originally Posted by Peritus

read this post:
http://www.mathhelpforum.com/math-he...ctorising.html

I Have tried and struggle to understand it

Originally Posted by duckegg911

Can anyone show me the way to solve this following equation by factorising, i need to see all workin out so i can fully understand, i've been pulling my hair out all day today. hope someone can help me.


2xsquared -5x - 7 = 0

Many Thanks
Chris

ok all u do is
i think u have learnt how to factorise quadratics the same way i have.
axsquared+bx+c
a= 2 b=-5 c=-7
a times c 2 times -7 is -14
so now u have to list all the factors of -14 until u find a pair that adds up to b which is -5.
1, -14
2, -7
7. -2
14, -1
2 plus -7 equals -5
so.... now u do the rest
can u remember it now? if u dont understand this way then i cant help u coz i have only learnt it like this, its possible maybe some1 else can help u tomorow

Originally Posted by duckegg911

I Have tried and struggle to understand it

these links might help:
MyMaths.co.uk - factorisemovie
and for more
MyMaths.co.uk - factorise Higher

Originally Posted by help_me

ok all u do is
i think u have learnt how to factorise quadratics the same way i have.
axsquared+bx+c
a= 2 b=-5 c=-7
a times c 2 times -7 is -14
so now u have to list all the factors of -14 until u find a pair that adds up to b which is -5.
1, -14
2, -7
7. -2
14, -1
2 plus -7 equals -5
so.... now u do the rest
can u remember it now? if u dont understand this way then i cant help u coz i have only learnt it like this, its possible maybe some1 else can help u tomorow
what year r u at school?

Hey thats great, what comes next?

Originally Posted by duckegg911

Hey thats great, what comes next?

so u have found -14's factors u know that u have to find a pair that add up to b which equals -5
2 and -7 add up to -5 so u put the pair into brackets such as

(2x - 7)(x + 2) = 0
then u expand the brackets
as in 2xsquared+2x-7x-14
then u simplify the equation into
2xsquared-12x-7(check this bit im not entirely sure about this)
hope it helps...............

Originally Posted by help_me

the links above will explain it far better than me try them first

i totally understand your previous description, please try to explain the rest of the stages

thanks

Originally Posted by help_me

so u put the pair in brackets

(2x - 7)(x + 1) = 0
then u expand them again
as in 2xsquared+2x-7x-7
then u simplify it down
im sure u can do that
the links above will explain it far better than me try them
hope it helps...............

Can you write the full solution as you would write it down ?

Originally Posted by duckegg911

Can you write the full solution as you would write it down ?

the answer is 2xsquared-12x-7

Originally Posted by help_me

the answer is 2xsquared-12x-7

Can anyone please confirm that this is infact the final answer?

Many thanks

Originally Posted by duckegg911

Can anyone please confirm that this is infact the final answer?

Many thanks

there is no more work required to solve the quadratic equation is there ?

Originally Posted by duckegg911

there is no more work required to solve the quadratic equation is there ?

So let's summarise:

The start: SOLVE

Where you are now: You've factorised and got .

(Note the typo in post #7)

The finish: You have to SOLVE .

In case you missed it, the key word in finishing the question is SOLVE:

Either ,

Or .

So the SOLUTION to is .

Now there's no more work required.