# Thread: Quadratic Equations By Factorising

1. ## Quadratic Equations By Factorising

Can anyone solve the following Quadratic equation by using factorising?

2xSquared - 5x - 7 = 0

Cheers

2. Originally Posted by duckegg911
Can anyone solve the following Quadratic equation by using factorising?

2xSquared - 5x - 7 = 0

Cheers
$\displaystyle 2x^2 - 5x - 7 = 0$

$\displaystyle (2x - 7)(x + 1 ) = 0$

$\displaystyle x = \frac{7}{2}$

OR

$\displaystyle x = -1$

3. Originally Posted by janvdl
$\displaystyle 2x^2 - 5x - 7 = 0$

$\displaystyle (2x - 7)(x + 1 ) = 0$

$\displaystyle x = \frac{7}{2}$

OR

$\displaystyle x = -1$
Many Thanks for the reply, is there any chance you can explain the steps?

Cheers

4. Originally Posted by duckegg911
Many Thanks for the reply, is there any chance you can explain the steps?

Cheers
You don't know how to factorise?

5. Originally Posted by janvdl
You don't know how to factorise?
The questions are to help my son, so no i dont maths isnt my strong point im afraid

6. Originally Posted by duckegg911
The questions are to help my son, so no i dont maths isnt my strong point im afraid
Does he know how to factorise?

If he does, he simply needs to find the value of $\displaystyle x$ in each bracket seperately after factorising, so that one of the brackets is equal to $\displaystyle 0$.

In other words:

If we had $\displaystyle (x - 3)(x + 4) = 0$

Then for the first bracket $\displaystyle x - 3 = 0$ and for the second bracket $\displaystyle x + 4 = 0$

7. Originally Posted by janvdl
Does he know how to factorise?

If he does, he simply needs to find the value of $\displaystyle x$ in each bracket seperately after factorising, so that one of the brackets is equal to $\displaystyle 0$.

In other words:

If we had $\displaystyle (x - 3)(x + 4) = 0$

Then for the first bracket $\displaystyle x - 3 = 0$ and for the second bracket $\displaystyle x + 4 = 0$
now i am confused - SORRY

8. Originally Posted by duckegg911
now i am confused - SORRY
Is it possible for your son to sit with you and look at the explanations?

If ONE of the brackets = 0 then it will satisfy the equation. Then we only need to find another value for x to get the second bracket equal to 0 too.

9. Originally Posted by janvdl
Is it possible for your son to sit with you and look at the explanations?

If ONE of the brackets = 0 then it will satisfy the equation. Then we only need to find another value for x to get the second bracket equal to 0 too.
Ok thats starting to make sense now, the factorising bit.

10. Originally Posted by duckegg911
Ok thats starting to make sense now, the factorising bit.
So is there any other part where you feel you could benefit from a bit more explaining?

11. Originally Posted by duckegg911
The questions are to help my son, so no i dont maths isnt my strong point im afraid
Does your son have a set of class notes or tetxbook that covers factorising?

12. ## Final Answer

Originally Posted by janvdl
So is there any other part where you feel you could benefit from a bit more explaining?
is the final answer to solving this quadratic equation

2xsquared - 12x -7

13. Originally Posted by duckegg911
is the final answer to solving this quadratic equation

2xsquared - 12x -7
See this thread.