Question

Factor: 5x^2+16x+3
My teacher taught me to do it by finding the factors of 3 that add to be 16.. but I couldn't do it for this one.

Answer 1

theres a more general way ...

given ax^2 + bx + c; find that factors of a*c that add to b

Answer 2

your teacher showed you on a case that a=1

Answer 3

step 1, assume it factors into the form:

(x /a) (x /a) and find that factors of ac to start filling in parts



, in this case

(x /5) (x /5), and 5*3 = 15, factors of 15 that add to 16, also notice that the last term is +, so we have -- or ++ to consider, since the middle term is +, we chose ++

(x + /5) (x + /5) , what factors of 15 add to get 16?

Answer 4

15 and 1

Answer 5

then lets fill those in

(x + 15/5) (x + 1/5)

now we reduce this setup

(x + 3) (x + 1/5)

if any factor is left with a fraction, put the bottom in front, back where we got it from that is ...

(x + 3) (5x + 1)

Answer 6

so thats the answer?

Answer 7

how do we chk if it is or not?

Answer 8

factor (x+3)(5x+1)

Answer 9

factor is not the proper term, but i assume you mean FOIL maybe? but yeah, see if it produces the original setup :)

Answer 10

FOIL! yeah! thats it lol and it is right it came back to 5x^2+16x+3

Answer 11

then it has to be correct;)