# Math Help - 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

2. ## Tried

Originally Posted by Peritus
I Have tried and struggle to understand it

3. 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

4. Originally Posted by duckegg911
I Have tried and struggle to understand it
MyMaths.co.uk - factorisemovie
and for more
MyMaths.co.uk - factorise Higher

5. 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?

6. 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
hope it helps...............

7. 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

8. 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 ?

9. Originally Posted by duckegg911
Can you write the full solution as you would write it down ?

10. Originally Posted by help_me

Many thanks

Originally Posted by duckegg911

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

12. Originally Posted by duckegg911
there is no more work required to solve the quadratic equation is there ?
So let's summarise:

The start: SOLVE $2x^2 - 5x - 7 = 0$

Where you are now: You've factorised $2x^2 - 5x - 7$ and got $(2x - 7)(x + 1)$.

(Note the typo in post #7)

The finish: You have to SOLVE $(2x - 7)(x + 1) = 0$.

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

Either $(2x - 7) = 0 \Rightarrow 2x = 7 \Rightarrow x = \frac{7}{2}$,

Or $(x + 1) = 0 \Rightarrow x = -1$.

So the SOLUTION to $2x^2 - 5x - 7 = 0$ is $x = \frac{7}{2}, \, -1$.

Now there's no more work required.