Thread: Quadratic Formula

Hi, I'm having a slight bit of trouble grasping the concept of the general quadratic formula, the part that involves surds.

I have the question: Simplify 2+2 to the square root of 5 divided by 2.

I also have a few other things i may need assistance on, but i'll start here.

Since you are dividing the two's both in the numerator and the denominator each of them cancel out and you are left with:

Originally Posted by Kangarooo

Hi, I'm having a slight bit of trouble grasping the concept of the general quadratic formula, the part that involves surds.

I have the question: Simplify 2+2 to the square root of 5 divided by 2.

I also have a few other things i may need assistance on, but i'll start here.

Is that 2 + 2^(sqrt(5)/2) ?

If so, there's not much to simplify.

2 + 2^(sqrt(5)/2) = 2(1 + 2^{(sqrt(5) - 2)/2})

qbkr21's interpretation works out nicer, so i'm guessing that's what the question should be. Please type your questions clearly, use brackets to show what belongs together, use / to show division and ^ to show powers

Originally Posted by Kangarooo

Hi, I'm having a slight bit of trouble grasping the concept of the general quadratic formula, the part that involves surds.

The quadratic formula is not a concept, it's just a formula. you just plug stuff into it to find the answer. the concept behind the quadratic formula is called completing the square, you will have to learn that method of solving quadratics as well.

The quadratic formula says:

Given a quadratic of the form
ax^2 + bx + c = 0
then the roots are given by the formula
x = [-b +/- sqrt(b^2 - 4ac)]/2a

so you just plug in the numbers in their respective positions.

e.g. Solve 2x^2 + 5x + 1 = 0
=> x = [-5 +/- sqrt(25 - 4(2)(1)]/2*2 = [-5 +/- sqrt(17)]/4
so x = [-5 + sqrt(17)]/4 or x = [-5 - sqrt(17)]/4

Note: the roots of a function of x are the x values that cause the function to be zero. so once we have a quadratic = 0, solving for x gives the roots

Re:

Ahh, i think my meaning was misinterpreted.

I mean by 2+2 to the square root of 5 divided by 2 as everything past the divide is the numerator, and the 2 is the dinominator

qbkr21, how did you make that picture, i would be able to show you if i had that program

Originally Posted by Kangarooo

Ahh, i think my meaning was misinterpreted.

I mean by 2+2 to the square root of 5 divided by 2 as everything past the divide is the numerator, and the 2 is the dinominator

qbkr21, how did you make that picture, i would be able to show you if i had that program

Is this what you mean? The program we use here is called MathType

Jhevon recommended it to me. It is called MathType 5. I am now obsessed with it...

Yes, thankyou all

Originally Posted by Kangarooo

Yes, thankyou all

Did you understand the process?

Re:

ah, wait, how does the second step of the quadratic formula work?

This one:

Originally Posted by Kangarooo

ah, wait, how does the second step of the quadratic formula work?

This one:

you split it in two. one answer is with the plus sign, the other is with the minus sign

so x = (4 + 2sqrt(10))/4 or x = (4 - sqrt(10))/4 ......and continue

I use LaTeX.

You can use the one they have on Wikipedia.
Use <math></math> to type code.

You can also use one they have on PlanetMath