# Thread: One of the factors is

1. ## One of the factors is

15x^2 + 17x - 4

2. One of the factors of WHAT is $\displaystyle 15x^2 + 17x - 4$?

Or are you asking how do you factorise $\displaystyle 15x^2 + 17x - 4$?

3. the question give me 5 answers :
a) 15x-1
b) 3x-4
c) 5x+1
d) 3x-1
e) 3x+4

4. But WHAT is the question? Is it asking you "which of these 5 choices is a factor of this expression?"

5. Originally Posted by hoanghai549
the question give me 5 answers :
a) 15x-1
b) 3x-4
c) 5x+1
d) 3x-1
e) 3x+4
Assuming the problem really is "which of these 5 choices is a factor of this expression?", start with each of them and think what must be the other factor. For example, if one factor were 15x- 1, the other would be of the form ax+ b. (15x- 1)(ax+ b)= 15ax+ (15b- a)x- b so we must have a*15= 15, b*1= 4. In that case, is 15b- a= 17?

(And I agree with Prove It- please state the full problem in the first post. Don't make us guess what it is.)