Math Is Fun Forum

Dayan

Guest

Quadratic Equation

I'm a little bit confused on what to do with this equation:
(x-2)( (2x^2)-x-15) )= (x-2)

I'm thinking if dividing x-2 on both sides of the equation then after equating it to zero, I'll go on factoring. Am I on the right track?

Hoping someone could help me... Thanks in advance.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Quadratic Equation

Hi;

Welcome to the forum!

Do not divide, rather use this idea.

Now say:

are you okay to go from here?

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Au101

Member

Registered: 2010-12-01

Posts: 353

Re: Quadratic Equation

That's very nicely done by bobbym, remember: dividing through by the unknown causes you to lose solutions.

Dayan

Guest

Re: Quadratic Equation

Thank you very much! Your idea's great. I'm confused on doing the division since I'm about to divide with a variable and in the case that my variable is two then then my equation will be undefined. I can continue the factoring part.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Quadratic Equation

Dividing will cause you to end up with egg on your face. Personally, I do not like eggs.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Au101

Member

Registered: 2010-12-01

Posts: 353

Re: Quadratic Equation

Yes If we were to divide by x - 2, we would get

But there is another solution:

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Quadratic Equation

Hi Au101;

Good to see you!

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Au101

Member

Registered: 2010-12-01

Posts: 353

Re: Quadratic Equation

Hi bobbym, nice to see you too! Sadly I haven't really had much time to spare recently, but I couldn't resist doing some quadratic equations - if only to dust off a few cobwebs, it took me a few minutes to complete the square correctly, if I'm honest, added rather than subtracted! I hope you're well?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Quadratic Equation

Hi;

I am just the same which is sort of depressing when you think about it.

Completing the square is a hoot of fun! I forget how to do it daily.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Au101

Member

Registered: 2010-12-01

Posts: 353

Re: Quadratic Equation

Hehe! Useful trick, though, I got rather good at it when I was doing complex numbers, but that was a while ago now and - after staring at 2x^2 - x - 16 = 0 for a little while before realising it wouldn't factorise, I set about trying trawl the method up from the bottom of my brain

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Quadratic Equation

Hi;

I generally use the formula now but use what you like.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.