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Mathematics 19 Online
OpenStudy (amtran_bus):

Quadratic formula

OpenStudy (amtran_bus):

ganeshie8 (ganeshie8):

arrange it in standard form \(\large ax^2 + bx + c\)

OpenStudy (amtran_bus):

I have it worked, but apparently I have something wrong.

OpenStudy (amtran_bus):

I got -H plus or minus 2 sqrt 6a

ganeshie8 (ganeshie8):

ohk lets see, \(\large ax^2 + bx + c = 0\) quadratic formula \(\large x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}\)

ganeshie8 (ganeshie8):

Given equation, \(\large 6x^2 + 12xh - A = 0\) \(a = 6\) \(b = 12h\) \(c = -A\)

ganeshie8 (ganeshie8):

substitute them in quadratic formula

ganeshie8 (ganeshie8):

\(\large x = \frac{-12h \pm \sqrt{(12h)^2 - 4(6)(-A)}}{2(6)}\)

ganeshie8 (ganeshie8):

does it look rihgt, so far ?

OpenStudy (amtran_bus):

Right. I get -12H\[\pm \sqrt{144-4(-A)(6)}\] all over 12

ganeshie8 (ganeshie8):

\(\large x = \frac{-12h \pm \sqrt{(12h)^2 - 4(6)(-A)}}{2(6)}\) \(\large x = \frac{-12h \pm \sqrt{(12h)^2 + 24A)}}{12}\)

ganeshie8 (ganeshie8):

\(\large x = \frac{-12h \pm \sqrt{(12h)^2 - 4(6)(-A)}}{2(6)}\) \(\large x = \frac{-12h \pm \sqrt{(12h)^2 + 24A)}}{12}\) \(\large x = -h \pm \frac{\sqrt{(12h)^2 + 24A)}}{12}\)

OpenStudy (amtran_bus):

\[-12H \pm12\sqrt{24A} \]

OpenStudy (amtran_bus):

over 12?

OpenStudy (amtran_bus):

So -H plus or minus...???

ganeshie8 (ganeshie8):

yes, and the thing inside squareroot, we can t do much as both are not like terms

OpenStudy (amtran_bus):

So would it be \[-H \pm 12\sqrt{24A}\]

OpenStudy (amtran_bus):

Or would that 12 cancel also?

ganeshie8 (ganeshie8):

nopes. its a + in between. so we cant pill that 144 out here is the thing :- \(\sqrt{a+b} \ne \sqrt{a} \sqrt{b}\)

ganeshie8 (ganeshie8):

\(\large x = \frac{-12h \pm \sqrt{(12h)^2 - 4(6)(-A)}}{2(6)}\) \(\large x = \frac{-12h \pm \sqrt{(12h)^2 + 24A}}{12}\) \(\large x = -h \pm \frac{\sqrt{(12h)^2 + 24A}}{12}\) \(\large x = -h \pm \frac{\sqrt{144h^2 + 24A}}{12}\)

ganeshie8 (ganeshie8):

it cant be simplified further

OpenStudy (amtran_bus):

Oh. I forgot the H was paired with the 12. Thats what I was dong wrong. Your a grade saver!

ganeshie8 (ganeshie8):

np :) good if u want u can take the bottom 12 inside, it wud become 144 and simplify - but its good the way it is now.

OpenStudy (amtran_bus):

Humm. Do I need to at least take the ^2 out?

ganeshie8 (ganeshie8):

u forgot the 12 in the bottom of radical

OpenStudy (amtran_bus):

ganeshie8 (ganeshie8):

smaller value : \(\large x = -h - \frac{\sqrt{144h^2 + A}}{12}\) larger value : \(\large x = -h + \frac{\sqrt{144h^2 + A}}{12}\)

OpenStudy (amtran_bus):

Oh. The 24.

OpenStudy (amtran_bus):

Why is the 24 all gone again?

ganeshie8 (ganeshie8):

smaller value : \(\large x = -h - \frac{\sqrt{144h^2 + 24A}}{12}\) larger value : \(\large x = -h + \frac{\sqrt{144h^2 + 24A}}{12}\)

ganeshie8 (ganeshie8):

that was a typo sorry. make the A capital... looks ur system is case sensitive

OpenStudy (amtran_bus):

In the help video for this problem here is what they did to a slightly different problem. Look how they simplified the discriminant.

ganeshie8 (ganeshie8):

yeah if u wanto simplify u can pull out 4 max thats all

ganeshie8 (ganeshie8):

\(\large x = -h \pm \frac{\sqrt{4 \times 36 h^2 + 4x6A}}{12}\)

ganeshie8 (ganeshie8):

\(\large x = -h \pm 2\frac{\sqrt{36 h^2 + 6A}}{12}\)

ganeshie8 (ganeshie8):

\(\large x = -h \pm \frac{\sqrt{36 h^2 + 6A}}{6}\)

OpenStudy (amtran_bus):

One final ?. Why is the max 4 and not 12?

ganeshie8 (ganeshie8):

cuz, 4 is the perfect square, when it comes out, it becomes 2

OpenStudy (amtran_bus):

Thanks.

ganeshie8 (ganeshie8):

is the submission successful ?

OpenStudy (amtran_bus):

One sec

ganeshie8 (ganeshie8):

\(\large x = -h \pm \frac{\sqrt{36 h^2 + 6A}}{6}\) is same as, \(\large x = -h \pm \sqrt{h^2 + \frac{A}{6}}\)

ganeshie8 (ganeshie8):

one of them should work

OpenStudy (amtran_bus):

It worked, the 1st one!!!

ganeshie8 (ganeshie8):

wow ! finally !! :)

OpenStudy (amtran_bus):

Thanks again.

ganeshie8 (ganeshie8):

np :D

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