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Mathematics 13 Online
pandasurvive:

Jimmy began deriving the quadratic formula as shown.

pandasurvive:

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Nnesha:

ahhh this is a fun question but don't have time rn :( ignore all the work on the pic just start from the 1st step Ax^2+Bx+C=0 complete the square

Hero:

Multiply \(\dfrac{b}{a}x\) by \(\dfrac{2}{2}\)

Hero:

That should be the next step.

pandasurvive:

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pandasurvive:

@Hero

Hero:

I know the correct answer but I cannot tell you what it is outright.

pandasurvive:

@hero ok

pandasurvive:

@hero how can i find the answer?

Hero:

One of the answer choices gives away the explanation.

Hero:

But the truth is the actual next step (what I mentioned above) is not included in the answer choices.

Hero:

One cannot proceed without conducting that particular step.

pandasurvive:

Subtract x² from each side?

Hero:

They give you the following steps: \(ax^2 + bx + c = 0\) Divide both sides by a: \(x^2 + \dfrac{bx}{a} + \dfrac{c}{a} = 0\) Subtract \(\dfrac{c}{a}\) from both sides: \(x^2 + \dfrac{bx}{a} = -\dfrac{c}{a}\) Add \(\left(\dfrac{b}{2a}\right)^2\) to both sides: \(x^2 + \dfrac{bx}{a} + \left(\dfrac{b}{2a}\right)^2 = -\dfrac{c}{a} + \left(\dfrac{b}{2a}\right)^2\)

Hero:

At this point, you're supposed to know to multiply the middle term of the left hand side by \(\dfrac{2}{2}\) to get: \(x^2 + \dfrac{2b}{2a}x + \left(\dfrac{b}{2a}\right)^2 = -\dfrac{c}{a} + \left(\dfrac{b}{2a}\right)^2\)

pandasurvive:

Thats not a choice though.

Hero:

I'm not done yet

Hero:

Then you would split the middle term to get: \(x^2 + \dfrac{b}{2a}x + \dfrac{b}{2a}x +\left(\dfrac{b}{2a}\right)^2 = -\dfrac{c}{a} + \left(\dfrac{b}{2a}\right)^2\) Then expand \(\left(\dfrac{b}{2a}\right)^2\) to get: \(x^2 + \dfrac{b}{2a}x + \dfrac{b}{2a}x +\dfrac{b^2}{4a^2} = -\dfrac{c}{a} + \dfrac{b}{4a^2}\)

Hero:

Then: \(x\left(x + \dfrac{b}{2a}\right) + \dfrac{b}{2a}\left(x + \dfrac{b}{2a}\right) = -\dfrac{c}{a} + \dfrac{b}{4a^2}\)

Hero:

And then you factor the common term on the left hand side of the equation to get: \(\left(x + \dfrac{b}{2a}\right)\left(x + \dfrac{b}{2a}\right) = -\dfrac{c}{a} + \dfrac{b}{4a^2}\) Which simplifies to \(\left(x + \dfrac{b}{2a}\right)^2 = -\dfrac{c}{a} + \dfrac{b}{4a^2}\)

Hero:

All of that is the process of factoring the trinomial.

Hero:

There's a typo in the steps unfortunately.

Hero:

The steps are correct otherwise

Ultrilliam:

hey hero, if you tell me what the error is i'll fix it ._.

Hero:

On the right hand side, the last term should be \(\dfrac{b^2}{4a^2}\) everywhere you see \(\dfrac{b}{4a^2}\)

Hero:

@pandasurvive are you good now?

Ultrilliam:

http://prntscr.com/f32ir5 so like this?

Ultrilliam:

And panda is currently AFK

Hero:

No, that doesn't look right.

Hero:

Don't worry about it @Ultrilliam

Ultrilliam:

ok then ._.

Hero:

Just try to work on the edit button. It would greatly improve the quality of my responses.

pandasurvive:

@hero thank you

Hero:

You're most welcome. Anytime

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