x^2- 15x + 36 = 0 x = ?...Help?

Question

I thought the answer to this was (1,0). My teacher said it was wrong. She said the answer is either {2, 18}...

...{3, 12}

...{2, 36}

...{4, 0}

I tried figuring it, I can get one of those answers though.

Answer 1

Here's what I think you should try:

Think what two numbers multiplied together will give 36. You have lots of choices...eg 36 x 1 and 9 x 4 and 6 x 6 and 12 x 3 and -36 x -1 and -9 x -4 and -6 x -6 and -12 x -3.

now since the middle number is -15, this means that the two numbers need to add up together to make -15 (and multiply together to get 36).

so now think...what two numbers multiplied together will make 36, provided that those two numbers will add together to get -15?

and here is the only choice: -12 x -3

-12 x -3 = 36
-12 -3 = -15

Therefore the two factors are -12 and -13...

and now think what two numbers multiplied together will give x squared?

the only one to choose is x and x

so your factors need to be: (x-12) (x-3)

now set each of these factors equal to zero:

x - 12 = 0
x - 3 = 0

and solve for x...

x = 12
x = 3

these are the only two solutions

...and you can prove it by checking it:

substitute 12 into the equation and you should get 0 = 0
and now substitute 3 into the equation and you should also get 0 = 0

so your two solutions for x are 12 and 3

I hope this helps...

Answer 2

x to the power of 2 minus 15 plus 36 equal to 0?
(x- 12) (x-3 )=0 there fore your answer is {3, 12}

You have to factor the problem and since it's a perfect square and the equation is already equal to 0 all you have to do is seperate and make sure that you have no variables squared at the end. Just set each equation seperately equal to zero: like
x-12=0 x-3=0
+12=+12 +3=+3
x=+12 x= +3
and you get your answers. IF you need any more help with your math homework and you don't want to waste points online, email me! [e-mail]

Answer 3

The answer is {3,12} because when x is put in the quadratic formula, x = 3 and 12

quadratic formula
x = negative b, plus or minus the square root of b squared minus four a times c divided by two a

x = (-b +/- square root [b^2 - 4ac]) / 2a

a = 1 (the coefficient in front of x^2)
b = -15 (the coefficient in front of x)
c = 36 (the last coefficient)

negative 15 times a negative is positive 15
plus/minus the square root of 15^2 which is 225 minus 4 times 1 times 36 which is 144
225 - 144 is 81. The square root of 81 is 9
15 + 9 is 24. Divide 24 by 2 times one (which is two) and get 12.
15 - 9 is 6. Divide six by 2 and get three.

x = 3, 12

Answer 4

Looks like {3,12} to me. =)

Get something that adds up to 15 and gets the product of 36. ^^

Go with (x-3) (x-12)

Why? Because the 15 is negative, and -3+-12 = -15
Also, -3x-12=36.

yay <333

Answer 5

{3, 12}
x^2- 15x + 36 = 0
like the other quadratic question you posted,
find the factors.
In this case, -3 and -12
(x-12)
(x-3)
(x-12)(x-3) = 0
x-12=0
or
x-3=0
---------
x-12=0
x=12
or
x-3=0
x=3

Answer 6

First factor:

x²-15x+36 = (x-12)(x-3)

so x=3 or x=12.

Answer 7

the 0x is just extra info. Just factor the equation.

(x-3)(x-12)

so x=3 or 12

Answer 8

(x - 12).(x - 3) = 0
x = 3, x = 12 is answer.

Answer 9

(x-12)*(x-3) = 0

x=3 or x=12