You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**longman619****Member**- Registered: 2006-09-14
- Posts: 3

Hey, I'm having trouble with a few of these.

1. x^2 - 6x + 3 = 0

2. x^2 + 5x + 1 = 0

3. 2x^2 - 50 = 0

4. x = 3/x + 7

Offline

**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

Those are quadratic equations. It looks like they won't factorise, so you need to either complete the square of use the quadratic formula. The quadratic formula is quicker, so I recommend that way.

If ax² + bx + c = 0, then x = (-b ± √(b² - 4ac))/(2a).

(*Look at the post below for a clearer version of this. My LaTeX is terrible.*)

So in your first question, a = 1, b = -6 and c = 3, so x = (6 ±√(6² - 4*1*3))/2*1

This works out to be 3 ± √6.

Your other three questions can be worked out in exactly the same way. Number 4 needs a bit of rearranging first though.

Why did the vector cross the road?

It wanted to be normal.

Offline

**luca-deltodesco****Member**- Registered: 2006-05-05
- Posts: 1,470

to rewrite in latex

for 4)

multiply by x*Last edited by luca-deltodesco (2006-09-22 08:16:46)*

The Beginning Of All Things To End.

The End Of All Things To Come.

Offline

**longman619****Member**- Registered: 2006-09-14
- Posts: 3

I get x=9.25 or x= 4.71 for number 4 - can someone check this

Offline

**Dross****Member**- Registered: 2006-08-24
- Posts: 325

longman619 wrote:

I get x=9.25 or x= 4.71 for number 4 - can someone check this

Ah, but the beauty of these questions is that you can check them yourself! Simply plug one of your values for x into the equation, and see if it works.

So if you wanted to check your solution of x = 9.25, you'd just see if:

was true or not. Unfortunately, I don't think your answer was correct - I get:

Bad speling makes me [sic]

Offline

Pages: **1**