Which of the following is a factor of 6x^2 + 2x – 21? explain?

Question

amistre64 · Answer

if it factors nicely ..... multiply the first and last coeffs; what do we get?

anonymous · Answer

-126?

amistre64 · Answer

and if we create a factor list of -126, we could find 2 factors that add to 2

anonymous · Answer

none?

amistre64 · Answer

then this wont factor nicely into rational numbers

anonymous · Answer

so is it prime?

amistre64 · Answer

its not prime, its just not rational ... itll contain a square root in it

anonymous · Answer

ok so what do i put for an answer?

amistre64 · Answer

6x^2 + 2x – 21 = 0

 6x^2 + 2x  = 21

 6(x^2 + 1/3x)  = 21

 6(x^2 + 1/3x + 1/36 - 1/36)  = 21

 6 (x+1/6)^2 - 6/36  = 21

 6 (x+1/6)^2  = 21 + 1/6

 (x+1/6)^2  = (21(6)+ 1)/36

 x+1/6  = +- sqrt(127)/6

 x  =[-1 +- sqrt(127)]/6

amistre64 · Answer

well considering it says "which of the following"; im not even sure what the options would be ...

anonymous · Answer

4x – 3

 2x + 7

 6x – 3

 None of the above

amistre64 · Answer

lol, then i know what id pick ....

amistre64 · Answer

it doesnt factor nicely into rationals;  and they give you 3 nice rational options

anonymous · Answer

so is it none of the above

amistre64 · Answer

im going with none of the above, yes

anonymous · Answer

thank you for explaining and not just giving an answer

amistre64 · Answer

its what i do best ... even when im trying to just give an answer lol