# Quadratic Equations By Factorising

• Jan 17th 2008, 06:35 AM
duckegg911
Quadratic Equations By Factorising
Can anyone solve the following Quadratic equation by using factorising?

2xSquared - 5x - 7 = 0

Cheers
:)
• Jan 17th 2008, 07:11 AM
janvdl
Quote:

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

2xSquared - 5x - 7 = 0

Cheers
:)

$2x^2 - 5x - 7 = 0$

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

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

OR

$x = -1$
• Jan 17th 2008, 07:20 AM
duckegg911
Quote:

Originally Posted by janvdl
$2x^2 - 5x - 7 = 0$

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

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

OR

$x = -1$

Many Thanks for the reply, is there any chance you can explain the steps?

Cheers
• Jan 17th 2008, 07:30 AM
janvdl
Quote:

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?
• Jan 17th 2008, 07:38 AM
duckegg911
Quote:

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 :)
• Jan 17th 2008, 07:43 AM
janvdl
Quote:

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 $x$ in each bracket seperately after factorising, so that one of the brackets is equal to $0$.

In other words:

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

Then for the first bracket $x - 3 = 0$ and for the second bracket $x + 4 = 0$
• Jan 17th 2008, 08:18 AM
duckegg911
Quote:

Originally Posted by janvdl
Does he know how to factorise?

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

In other words:

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

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

now i am confused - SORRY
• Jan 17th 2008, 08:20 AM
janvdl
Quote:

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.
• Jan 17th 2008, 08:25 AM
duckegg911
Quote:

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.
• Jan 17th 2008, 08:28 AM
janvdl
Quote:

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?
• Jan 17th 2008, 12:01 PM
mr fantastic
Quote:

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?
• Jan 20th 2008, 02:53 PM
duckegg911
Quote:

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
• Jan 20th 2008, 05:25 PM
mr fantastic
Quote:

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

2xsquared - 12x -7