Question

find DOMAIN of X.
f(x)=2x/10x^2+13x-3

i forgot how to factor the bottom please help??

Answer 1

the answer is all real numbers except -3/2 and 1/5

i just forgot how to do it??

Answer 2

10x^2 + 13x - 3 = (5x-1)(2x+3)

Answer 3

x=R\{1/5,-3/2}

Answer 4

but im asking how do i factor it??

Answer 5

didn't i just show how to factor the denominator?

Answer 6

how do i know to get 5x-1 and 2x+3??

Answer 7

most of the time i just use the rules of FOIL...
Inside + Outside = 13
First * Last = -3

a lot of it is trial/error but it's not a total shot in the dark....

Answer 8

if it is factorable -> 10x^2 must be either 10x*x or 2x*5x
then you can easily see that 2*5 is good and you add -1 and +3 just so it equals the expression

Answer 9

also, since the answer was given to you, you know that the bottom can be thought of as:
(x - 1/5) (x + 3/2)

Answer 10

thanks yall, but i know theres a rule i just cant seem to remember it

Answer 11

Forget about "rules" use your common sense... maths is about brain... You can make up rules if you want, but it is not neccesary...
(Ax+B)(Cx+D)=ACx^2+(BC+AD)x+BD .... crap