Can someone please show me the steps in solving 36=(x-9)(x)?

Question

I know that the ans would be x=12, but can someone show me the logical equation steps to solve it. Thx !

We just learned this at school and I had a brain freeze....your responses really helped ...thx

Answer 1

36=(x-9)(x)
multiply out the brackets gives
36=x^2-9x
set it equal to zero
x^2-9x-36=0
factor it back into brackets
(x+3)(x-12)=0
so either (x+3)=0 or (x-12)=0
so x is either -3 or else it's 12

Answer 2

x = 12 is one answer; the other one is x = -3.

To solve this, first expand the product on the right hand side. Then put it in the standard quadratic form and factorise it.

36 = (x-9)(x)
=> 36 = x.x - 9.x
=> x^2 - 9x - 36 = 0
=> (x - 12) (x + 3) = 0
=> x - 12 = 0 or x + 3 = 0
=> x = 12 or -3.

If you can't factorise the equation, there is a formula:
if ax^2 + bx + c = 0
then x = (-b +/- sqrt(b^2 - 4ac)) / (2a)
assuming that b^2 - 4ac >= 0 (if this is negative there are no [real] solutions; there are what are called complex solutions, but that's a way off from where you are yet.)

Here 1.x^2 + (-9).x + (-36) = 0
so a = 1, b = -9, c = -36.
So the answers are
x = [-(-9) +/- sqrt((-9)^2 - 4.1.(-36))] / (2.1)
= [9 +/- sqrt(81 + 144)] / 2
= (9 +/- sqrt(225)) / 2
= (9 +/- 15) / 2
= 24/2 or -6/2
= 12 or -3.

Answer 3

2x+9=31 2x+9 -9 =31-9 2X=22 2x/2= 22/2 x-11 5x-7=38 5x-7+7=38+7 5x=40 5 5x/5=40 5/5 x=9 12-x=21 12=21+x 21-12=x x=9 ...the rest you're able to do on ur very own, merely stick to my occasion, or you will not discover out a thank you to do it precise and could do undesirable in an prolonged time =]

Answer 4

36=(x-9)(x
36=x^2-9x (distributive property)
x^2-9x-36=0(subtract 36)

2 numbers that multiply to -36 and add up to -9

-12 and 3
(x-12)(x+3)

x= 12 and -3

-3 is not needed if you are trying to find a length of something.

Answer 5

36 = (x - 9) * (x)
36 = x^2 - 9x
0 = x^2 - 9x -36
which is the same as:
x^2 - 9x -36 = 0

now you factor this into
(x + 3) * (x - 12) = 0
and so the answer is 12 and -3

Answer 6

36 = x^2 - 9x
x^2 -9x -36 = 0
(x-12)(x+3)=0
x=12 or x=-3

Answer 7

36=(x-9)(x)
36=x^2-9x
x^2-9x-36=0
(x-12)(x+3)=0
x-12=0, x=12
x+3=0, x=-3

{x:x=-3 and 12}

Answer 8

36=(x-9)(x)
36=x(squared)-9x
square root sign on both sides of the equation
6=x-3x
6=-2x
divide by -2
answer=-3 but 12 would work too...i guess...how'd you get 12?

Answer 9

i hope your not cheating on your homework...but its: (xx = squared)

x(x-9) = 36
xx - 9x = 36
and if you need it further then...
xx/9 - x = 4
it kant really get any further...

Answer 10

What does the directions say?