Math 8th Grade
posted by Lana Von Monroe on .
The chart below shows an expression evaluated for four different
values of x
x: x2+x+5:
1 7
2 11
6 47
7 61
Josiah concluded that for all positive values of x, x2+x+5 produces a prime number. Which value of x serves as a counterexample to prove Josiahâ€™s conclusion false?
A: 5
B: 11
C: 16
D: 21

Try each one see which one isn't prime. You won't have to go far down the list.