C1 - Proof for Quadratic Formula Required?

Inflation

As title, the (b2+-/b2-4ac)/2a

Do we need to know how to get to that?

Thanks :smile:

A bit late, I know :frown:

Reply 1

Rabite

I doubt it.
But completing the square is something required for your arsenal.
(The quadratic formula is just the general case of completing the square)

Reply 2

doG1

no! you dont need to know any proofs, just how to use them. C1 is basically GCSE - dont worry!

Reply 3

chidona

Rabite

I doubt it.
But completing the square is something required for your arsenal.
(The quadratic formula is just the general case of completing the square)

No, you just need to memorise the quadratic equation.
Hell, i don't know anyone who knows the proof for the Q.E.

Reply 4

Inflation

Rabite

I doubt it.
But completing the square is something required for your arsenal.
(The quadratic formula is just the general case of completing the square)

Yeah, I can complete the square.

Hopefully they won't ask :smile:

Thanks...., you should have gender symbol, I assume you are a girl? ;D

Reply 5

zrancis

ax^2+bx+c=0

x^2+\frac{bx}{a}+\frac{c}{a}=0

(x+\frac{b}{2a})^2-(\frac{b}{2a})^2+\frac{c}{a}=0

(x+\frac{b}{2a})^2=\frac{b^2}{4a^2}-\frac{c}{a}

(x+\frac{b}{2a})^2=\frac{b^2-4ac}{4a^2}

x+\frac{b}{2a}=\pm\frac{\sqrt{b^2-4ac}}{2a}

x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}

Edit: you wont need to be able to do that for C1 or C2.

Reply 6

Jim_5_Bob

all the text books say you need to be able to but I have never seen it as a question before

Reply 7

leesto

Jim_5_Bob

all the text books say you need to be able to but I have never seen it as a question before

I can remember learning it for my C1 exam and vaguely remember it coming up in a past paper I did - although this could possibly have been a Solomon paper.