Factor completely 3x^2 + x + 7.

(3x + 1)(x + 7)

(3x + 7)(x + 1)

Prime

(3x + 4)(x + 3)

Question

Factor completely 3x^2 + x + 7.

(3x + 1)(x + 7)

 (3x + 7)(x + 1)

 Prime

 (3x + 4)(x + 3)

anonymous · Answer

@geerky42 can you help?

geerky42 · Answer

Try to FOIL A, B, and D. if none of them matches $3x^2 + x + 7$, then answer is C.

mathstudent55 · Answer

This is a method for factoring trinomials of the form $ax^2 + bx + c$, where $a\ne 1$.

mathstudent55 · Answer

First, multiply a and c.
In your case, a = 3, and c = 7.
What is 3 * 7 = ?

anonymous · Answer

21

anonymous · Answer

@mathstudent55

mathstudent55 · Answer

Good.

mathstudent55 · Answer

Now we use 21, and we need two numbers that multiply to 21 and add to b.
In your case, b = 1.
So, once again, you need to numbers that multiply to 21 and add to 1.
Can you find two such numbers?

anonymous · Answer

no, because it would only be 3x7 really

anonymous · Answer

would it be prime @mathstudent55

mathstudent55 · Answer

Sorry. My computer went nuts.
I'm back now.

anonymous · Answer

OKay, Its fine :)

mathstudent55 · Answer

You are correct.
The only factors of 21 are 3 * 7 and 1 * 21 (and the negative pairs -3 * (-7) and -1 * (-21)).

None of those choices give you a sum of 1. That means the trinomnial can't be factored, and it's prime.

anonymous · Answer

Thank you For your help @mathstudent55 :D

mathstudent55 · Answer

You're welcome.