SOLUTION: Which expression is prime? A x2 - 14x + 49 B x2 + 14x + 49 C x2

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Question 1149468: Which expression is prime?
A
x2 - 14x + 49
B
x2 + 14x + 49
C
x2 - 2x + 49
D
x2 + 2x + 1
and how
Found 2 solutions by Boreal, ikleyn:
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website!
first is (x-7)^2
second is (x+7)^2
D is (x+1)^2
it is C
look at the discriminant, sqrt (b^2-4ac)
it is prime if that is the sqrt of a negative number
C has a discriminant of sqrt ((-2)^2-196), which is sqrt (-192), a complex number.

Answer by ikleyn(52833)   (Show Source):
You can put this solution on YOUR website!
.

In his post, @Boreal incorrectly calls discriminant as   sqrt(b^2-4ac).

Actually, the discriminant of the quadratic equation is   b^2-4ac.

The rest of the solution by @Boreal is correct.

SOLUTION: Which expression is prime? A x2 - 14x + 49 B x2 + 14x + 49 C x2 - 2x + 49 D x2 + 2x + 1 and how