Math help?

Question

how do i factor x^2-7x-18 ? Please give a detailed answer because i know nothing about math.

Answer 1

You look for two numbers a and b that when multiplied together give -18, and when added together, -7.
For example:
1 -18
2 -9
3 -6
6 -3
9 -2

So we choose 2, -9, because they satisfy the conditions, and the answer is simply
(x+2)(x-9)

Answer 2

Alright, to factor x^2-7x-18. First, multiply the coefficients of the leading term (ie the monomial with the highest power) and the term independent of x (ie 18). so, in this case 1 * 18 = 18. (let * be the multiplication sign)
Now, ask yourself, what to factors of 18 subtract to give you - 7? (you know to subtract by the fact that there is a subtraction sign between the 7x and the 18)
Well, the factors of 18 are: 1, 2, 3, 6, 9, and 18. Well, 9 - 2 = 7 so.
Rewrite the trinomial as....
x^2 - 9x + 2x - 18 (because -9x - -2x = - 7x)
Now, factor the first two terms and the last two terms.....
x ( x - 9 ) + 2 ( x - 9 )
since both mathematical expressions inside the parenthesis are the same, you've chose the right factors of 18....
now, simply rewrite the expression as
( x - 9 ) ( x + 2 )
the x is in front of the ( x - 9 ) and the +2 is in front of the other ( x - 9 )
therefore the answer is
( x - 9 ) ( x + 2 )

Answer 3

x^2-7x-18
First, multiply the coefficient of the first term with the last term.
1*-18 = -18
Now you need to find two factors of - 18 that add up to -7
It is obvious that one of the factors is negative. It's also clear that the larger one is negative as the sum of the two if negative (-7).
Let's consider the possibilities:
1*-18
2*-9
We can stop here as we have our answer
2-9 = -7
Now we need to split the middle term accordingly
x^2-7x-18 = x^2+2x-9x-18
= x(x + 2) - 9(x + 2)
= (x-9)(x+2)

Answer 4

you can do this in simple steps:
1. find the factors that multiply to equal -18 and at the same time add to equal -7 in this equation the factors would by 9 and 2. ( -9x2=-18 and -9+2=-7)
2. then you have to set it into the correct form: (x-9)(x+2)
3. there you go! hope you figure these out they can get tricky!

Answer 5

well, break up the problem.

x^2(that is to the second power)-7x-18
so first write out the problem broken up

*=the multiplication sign
x^2=x*x...now plug it into the problem

x*x-7x-18
well first of all you can only simplify the problem because of the variable.

so where was i?...
x*x-7x-18
that is like 2 x's minus 7 x's. that would give you a negative 5x
so your answer would be negative 5x minus 18...do you understand it a little better now?
you would write that:
-5x-18

Answer 6

x^2-7x-18=0
make the factors of 1*18=18 which will sum or sub upto 7
we get 9-2=7
therefore
x^2-9x+2x-18
x(x-9)+2(x-9) take x-9 common
(x-9)(x+2)
therefore (x-9)(x+2) are the possible factors

Answer 7

x² -7x -18 =
(x - 9)(x +2)

Answer 8

step 1. turn on calculator
step 2 press factor
step 3 type in equation
step 4. press enter
horrah!

Answer 9

x^2-7x-18
(x+9)(x-2)
use foil

Answer 10

-5x-18