(x^2 + 4x) + (2x^2 - 6x)

To add these polynomials, we need to combine like terms.

We can start by adding the coefficients of x^2: 1x^2 + 2x^2 = 3x^2.

Next, we add the coefficients of x: 4x - 6x = -2x.

Putting it all together, the simplified sum is:

3x^2 - 2x.

(2x^2 + 3x) - (x^2 + x)

To subtract these polynomials, we distribute the negative sign across the second polynomial:

2x^2 + 3x - (x^2 + x)

= 2x^2 + 3x - x^2 - x

= (2x^2 - x^2) + (3x - x)

= x^2 + 2x.