quadratic equation from amazing lil boy

**pitt** · November 25th 2007, 11:01 AM

hi there i want help with this quadratic equation.. im quiet young.. so try to explain it step by step so i can understand

y= 2x3+3x+19

p.s. the first 3 is squared

can someone identify a b and c value?? Thanks very much.. try fully explain it to me so i can do it next time by myself.. thanks

**janvdl** · November 25th 2007, 11:11 AM

Originally Posted by pitt

hi there i want help with this quadratic equation.. im quiet young.. so try to explain it step by step so i can understand

y= 2x3+3x+19

p.s. the first 3 is squared

can someone identify a b and c value?? Thanks very much.. try fully explain it to me so i can do it next time by myself.. thanks

Did you mean $3x^2 + 3x + 19$ ?

A quadratic equation is in the format: $ax^2 + bx + c$

Do you want the equation solved?

$0 = 3x^2 + 3x + (19 - y)$ [That part in brackets is your c-value]

We know that $x = \frac{ -b +- \sqrt{b^2 - 4ac}}{2a}$

So simply set the values into the equation:

$x = \frac{ -(3) +- \sqrt{(3)^2 - 4(3)(19 - y)}}{2(3)}$

$x = \frac{ -(3) +- \sqrt{12y - 219}}{6}$

It seems that for this equation to be true, $y > 18,25$

**pitt** · November 25th 2007, 11:20 AM

i didnt understand anything :S

**janvdl** · November 25th 2007, 11:26 AM

Originally Posted by pitt

i didnt understand anything :S

Be more specific?

**pitt** · November 25th 2007, 11:32 AM

Where did u get the 4 from?? and why do you put numbers 3 on brackets??

**janvdl** · November 25th 2007, 11:35 AM

Originally Posted by pitt

Where did u get the 4 from?? and why do you put numbers 3 on brackets??

Have you heard about the quadratic formula yet?

**pitt** · November 25th 2007, 11:37 AM

Originally Posted by janvdl

Have you heard about the quadratic formula yet?

ye but i cant remember what the formula is.. do you mind if you explain it to me?? thanks

**janvdl** · November 25th 2007, 11:42 AM

Originally Posted by pitt

ye but i cant remember what the formula is.. do you mind if you explain it to me?? thanks

If you have the formula: $2x^2 + 3x + 4$ , then the 2 is your a value, the 3 is your b value, and the 4 is your c value.

Like i said before: quadratic equations are in the format: $ax^2 + bx + c$

I'm sure you understand that.

The quadratic formula: $x = \frac{ -b +- \sqrt{b^2 - 4ac}}{2a}$

Thats how the formula looks, and you have to learn that format.

Let's say we want to solve that equation at the top that i used to explain.

Then wherever there is an a, we substitute it with 2.
Wherever there is a b, we substitute it with 3.
Wherever there is a c, we substitute it with 4.

Do you understand?

**janvdl** · November 25th 2007, 11:52 AM

I'm just letting you know that I have to leave now. Sorry.

Soroban is around, he'll probably continue where I left off.

Have a good night.

**pitt** · November 25th 2007, 12:12 PM

ye thanks very much.. i understood almost evertyhing just want to know how did you get 12 and 219... can anyone explain it?? and then how did he get 18??

so

a value is= 3

b= 4

c = 19

am i right??

**pitt** · November 25th 2007, 01:10 PM

oh ye one more thing.. you said wherever theres an a, i should substitute it with a 2.. why if you look at number 2 theres a bracket after it with number 3.. but the equation shows 2a.. why did u put 2(3) instead of 2(2)

**bcherkas** · November 25th 2007, 06:43 PM

Originally Posted by pitt

hi there i want help with this quadratic equation.. im quiet young.. so try to explain it step by step so i can understand

y= 2x3+3x+19

p.s. the first 3 is squared

can someone identify a b and c value?? Thanks very much.. try fully explain it to me so i can do it next time by myself.. thanks

To be a quadratic equation, it needs x^2 in it, where the power symbol ^ is used to mean that x is to the power 2.

You can learn a lot by reading some worked out examples as well as entering your own at webgraphing.com:

Free Online Quadratic Equation Solver: Solve by Quadratic Formula

It will give you step by step walk through on any quadratic equation. To start you might just click the button for solving a random equation, just to see how it looks. Then enter your own and read the worked-out solution.

**Jhevon** · November 25th 2007, 06:44 PM

Originally Posted by janvdl

If you have the formula: $2x^2 + 3x + 4$ , then the 2 is your a value, the 3 is your b value, and the 4 is your c value.

Like i said before: quadratic equations are in the format: $ax^2 + bx + c$

I'm sure you understand that.

The quadratic formula: $x = \frac{ -b +- \sqrt{b^2 - 4ac}}{2a}$

Thats how the formula looks, and you have to learn that format.

Let's say we want to solve that equation at the top that i used to explain.

Then wherever there is an a, we substitute it with 2.
Wherever there is a b, we substitute it with 3.
Wherever there is a c, we substitute it with 4.

Do you understand?

use \pm to get $\pm$

**janvdl** · November 26th 2007, 04:10 AM

Originally Posted by pitt

oh ye one more thing.. you said wherever theres an a, i should substitute it with a 2.. why if you look at number 2 theres a bracket after it with number 3.. but the equation shows 2a.. why did u put 2(3) instead of 2(2)

Oh yes, it should be 2(2). Thanks for the spot.

Try to spend a little time on it yourself to see how i got the values there. I simplified everything under the root.

**CaptainBlack** · November 26th 2007, 04:33 AM

Originally Posted by pitt

hi there i want help with this quadratic equation.. im quiet young.. so try to explain it step by step so i can understand

y= 2x3+3x+19

p.s. the first 3 is squared

can someone identify a b and c value?? Thanks very much.. try fully explain it to me so i can do it next time by myself.. thanks

See this

RonL

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