how do u cross multiply this? i know the answer i just need to know the the working out.x²-x-2=?

Answer 1

2 numbers that multiply to form the constant in this case being (-2) and its multiples must add to the variable in front of x.

2*1=2

now make the multiples add to = -1

-2+1=-1 & -2*1=-2, my god it works out how proper

threfore (x-2)(x+1)=0

Answer 2

This isn't called cross multiplication. Cross multiplication is when you have two fractions and are attempting to figure out which fraction is larger. Then you would mulitply the bottom of one and the top of the other, then compare to the opposite top and bottom product. It's much easier to show on paper than it is to tell it. Anyway, what you are trying to do is the reverse of the FOIL system. When you start figuring the kind of system that you are asking about, you're teacher should have given you this....(x-2)(x+1) FOIL says to multiply the First terms in the parenthesis, then the Outer terms, then the Inner terms, then the Last terms. Then, you add the answers that you got from those operations, giving x^2, +x, -2x, and -2. Add like terms to get x^2-x-2. After learning to get this equation, it makes much more sense trying to do it backward. The point is to find the middle number, which in this case is -1(x), and you use the last number, -2 to get this number. You ask yourself, what times what gives me the last number,-2, but when I add the what and what together, it gives me the middle number, -1. -2 times 1 = -2, and -2 plus 1 = -1. That's how you get the numbers in the parenthesis, these numbers are the what and what from above. Confusing,huh. If you get it right, it will make sense. Good luck!

Answer 3

x²-x-2 =
(x - 2) (x + 1)

Answer 4

x² - x - 2
You know that the factors of -2 would be -1 and 2 OR 1 and -2

Since you have a -x in the middle, you need to choose the 1 and -2 set because that would give you the -x when you FOIL it out.

Which gives you...
(x - 2) (x + 1)

Answer 5

If you mean, "How do you factor this?"
There are only two integer possibilities:
-2=-1*2, -2=2*-1, so
(x-1)(x+2)
(x+1)(x-2)
One of these works, the other does not.

Answer 6

SIMPLY FINd THE ROOT IN THE EQUATION
................X^2-X-2=0

FROM THE WELKNOWN EQUATION

x=[-b+-sqrt(b^2-4*a*c)]/2*a and a=1 b=-1 c=-2


and you have
x1= [- -1+sqrt(1-4*1*-(2))]/(2*1)=2
x2= [- -1-sqrt(1-4*1*-(2))]/(2*1)=-1
and you have the answer
(x-2)*(x-(-1))=(x-2)*(x+1)

Answer 7

that's not cross multiplication! if you want factors, they're 2 and -1