math
posted by Anonymous on .
if the domain is the set of integers, the solution set of x^2 3x 4<0 is what?

What your question really asks for is,
"For what values of x does the corresponding parabola
y = x^2  3x  4 fall below the xaxis?"
let's find the xintercepts ....
x^2  3x  4 = 0
(x4)(x+1) = 0
x = 1 or x = 4
so the expression is < 0 for 1 < x < 4
or
(x+1)(x4) < 0
( x+1 >0 AND x4<0) OR ( x+1 < 0 AND x4>0)
( x>1 and x<4) OR (x<1 AND x > 4)
x>1 and x<4 OR (null set)
1 < x < 4 
thank you, so anything between 1 and 4 would be my answer? (0,1,2,3)?

yes.

Since your domain is integers, only the integers (0,1,2,3) satisfy the inequality. Otherwise, there would be an infinite number of noninteger solutions between 1 and 4.