Let f(x)= 5/x and g(x)= 2x^2 + 5x. What 2 numbers are NOT in the domain of f o g?

Question

A. 0,-5/2

B. 0,-2/5

C. 0,2/5

D. 0,5/2

Answer 1

f o g = 5/(2x²+5x)

however, since you can't divide a number by 0,

The solution does not exist for (2x²+5x) = 0

So, let's see which values of x that includes

2x²+5x = 0 

x(2x + 5) = 0

x = 0 or 2x + 5 = 0   

             2x = -5

               x = -5/2

So, for x = 0 or x = -5/2 there is no solution so these numbers are not in the domain