How do you factor 2x^2 + 21x + 102x2+21x+10?

1 Answer
Mar 3, 2017

(2x+1)(x+10)(2x+1)(x+10)

Explanation:

To factorise 2x^2+21x+102x2+21x+10 we need to find two integers pp and qq such that:

(2x+p)(x+q) -= 2x^2+21x+10(2x+p)(x+q)2x2+21x+10

2x^2+(p+2q)x +pq -= 2x^2+21x+102x2+(p+2q)x+pq2x2+21x+10

:. pxxq = 10 and 2q+p=21

Considering factors of 10: 1xx10, 2xx5

By inspection we see that p=1 and q=10 satisfy the conditions.

Hence: 2x^2+21x+10 = (2x+1)(x+10)

Please note: After some practice, for simple quadratic functions that can be expressed as two linear factors, as in this example, you should be able to factorise the the function by inspection - without the need to express the logic above in written form. However, you will still perform the equivalent logic mentally.