Question

(-10/7) + 1/6 , once you find the LCD, do you add or subtract?

Answer 1

Since both fractions have the same denominator, you can simply add up (or substract) the numerators and keep the denominator unchanged :

x2+3x+2x2−16+3x+6x2−16=(x2+3x+2)+(3x+6)x2−16

=x2+6x+8x2−16.

Then, you can factorize it :

x2+6x+8x2−16=(x+2)(x+4)(x+4)(x−4)=x+2x−4.

In the case of a substraction :

x2+3x+2x2−16−3x+6x2−16=(x2+3x+2)−(3x+6)x2−16

=x2−4x2−16=(x+2)(x−2)(x+4)(x−4).