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
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
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
these links might help:
MyMaths.co.uk - factorisemovie
and for more
MyMaths.co.uk - factorise Higher
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...............
So let's summarise:
The start: SOLVE $\displaystyle 2x^2 - 5x - 7 = 0$
Where you are now: You've factorised $\displaystyle 2x^2 - 5x - 7$ and got $\displaystyle (2x - 7)(x + 1)$.
(Note the typo in post #7)
The finish: You have to SOLVE $\displaystyle (2x - 7)(x + 1) = 0$.
In case you missed it, the key word in finishing the question is SOLVE:
Either $\displaystyle (2x - 7) = 0 \Rightarrow 2x = 7 \Rightarrow x = \frac{7}{2}$,
Or $\displaystyle (x + 1) = 0 \Rightarrow x = -1$.
So the SOLUTION to $\displaystyle 2x^2 - 5x - 7 = 0$ is $\displaystyle x = \frac{7}{2}, \, -1$.
Now there's no more work required.