Math Is Fun Forum

Spanky

Member

Registered: 2010-02-24

Posts: 62

Writting an Equation

Write an equation for:

Quadratic with only one zero at the vertex point (-9,0) that is everywhere negative.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Writting an Equation

Hi Spanky;

A parabola has either 2 real roots or no real roots. It cannot have one zero, but it can have 2 identical roots.

The simplest way now is:

(x+9)(x+9) = x^2 + 18 x + 81, now negate all the coefficients to make y always negative.

-x^2 -18 x - 81 is one answer. It has a vertex at (-9,0) and is always negative.

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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.

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Writting an Equation

Write an equation for:

Quadratic with only one zero at the vertex point (-9,0) that is everywhere negative.

I know bobbym has kindly helped you out here, but this is your second time here now. Are you actually putting any of your own effort into doing your own homework, or just waiting for nice people like bobbym to give you something for you to copy?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Writting an Equation

Hi Jane;

Some things to add:

My brain says:

As usual you keep me guessing by having to fathom why you are underlining my username. As you know best, I do like to solve all types of problems. As you also know, I pick many and solve few. Thirdly, you know that I am not kind, I am vicious. Lastly, anyone who would blindly copy down my answers is dipping their unprotected hand into a bag of scorpions.

My emotions say:

Thanks as always.

Hi Spanky;

Jane is correct, you must try very hard on your own before asking anyone for help. I always assume that the questioner has already done that, if I am wrong then her comments have done you more good than 100 answers of mine.

P.S. Jane have you checked your guided exercises thread?

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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.