Question

(а+1) (а+2)-(а+1)(а-2)-а-1

Answer 1

If you would like to calculate (a + 1) * (a + 2) - (a + 1) * (a - 2) - a - 1, you can do this using the following steps:

(a + 1) * (a + 2) - (a + 1) * (a - 2) - a - 1 = a^2 + 2 * a + 1 * a + 2 - (a^2 - 2 * a + 1 * a - 2) - a - 1 = a^2 + 3 * a + 2 - a^2 + 2 * a - 1 * a + 2 - a - 1 = 3 * a + 3

The correct result would be 3 * a + 3.

Answer 2

$\displaystyle (a+1)(a+2)-(a+1)(a-2)-a-1= \\ =a^2+2a+a+2-(a^2-2a+a-2)-a-1= \\ =\not a^2+2a+a+2-\not a^2+2a-a+2-a-1=\boxed{3a+3}$