Question

x^2-5x-36 Use Quadratic Formula

Answer 1

\[{x_{1/2}} = \frac{{ - b \pm \sqrt {{b^2} - 4ac} }}{{2a}}\]

Answer 2

its not the answer it has to come out to a answer

Answer 3

a Number

Answer 4

ahh.. I thought you don't know the formula :F lol...

Answer 5

lol yea

Answer 6

x^2 - 5x - 36.

x = 5 + or - sqrt(25-4(36))/ 2

5/2 +/- sqrt(119)/2 i

This has complex roots so you can't get a real number.

Hope this helps :)

Answer 7

you have:
\[\LARGE x^2-5x-36=0\]
now substitute:
\[\LARGE {x_{1/2}} = \frac{{ - b \pm \sqrt {{b^2} - 4ac} }}{{2a}}\]

\[\large {x_{1/2}} = \frac{{ - (-5) \pm \sqrt {{25} - 4(-36)} }}{{2}}\]
can you do it now ? :)

Answer 8

18/2 and -8/2

Answer 9

Sorry, I forgot it was -36.

Follow @Kreshnik. I don't know how to do it like that!

Answer 10

@hoggard1020 need more help? :)

Answer 11

hoggard,

you ok now?

Answer 12

@thomasj, this simplifies down to 9 and -4!

Answer 13

yes its diffucult

Answer 14

ahh don't worry, it's pretty easy, you'll see ;)

\[\LARGE {x_{1/2}} = \frac{{ - (-5) \pm \sqrt {{25} - 4(-36)} }}{{2}}\]

\[\LARGE {x_{1/2}} = \frac{{ 5 \pm \sqrt {{25} +144} }}{{2}}\]
\[\LARGE {x_{1/2}} = \frac{{ 5 \pm \sqrt {{169}} }}{{2}}\]
\[\LARGE {x_{1/2}} = \frac{{ 5 \pm 13 }}{{2}}\]

NOW YOU HAVE:
\[\LARGE {x_{1}} = \frac{{ 5 - 13 }}{{2}}\]
AND
\[\LARGE {x_{2}} = \frac{{ 5 + 13 }}{{2}}\]
GO FOR IT...

Answer 15

Thanks =)

Answer 16

in the end you should have @tommo_lcfc 's result :)

Answer 17

OUR pleasure xD

Answer 18

I would not use the quadratic formula normally unless the equation could not be factorised.
In this case, it can be as 9 and -4 are suitable factors of 36 summing to 5 and producing -36 when multiplied. If the question says to use the quadratic formula as it did, you obviously should use it but if not, factorise if you can because that is easier and less time consuming.

Answer 19

in my opinion

Answer 20

@tommo_lcfc it saves time when you have simple quadratic formula... how about this: can you factorize this out?
\[\LARGE x^2-14x-72=0\]

Answer 21

OK, you win this round.