Simplify (3x^2-x+1)+(15-9x-2x^2)

$(3 x^{2} - x + 1) + (15 - 9 x - 2 x^{2})$

Remove parentheses.

$3 x^{2} - x + 1 + 15 - 9 x - 2 x^{2}$

Subtract $2 x^{2}$ from $3 x^{2}$ .

$x^{2} - x + 1 + 15 - 9 x$

Subtract $9 x$ from $- x$ .

$x^{2} - 10 x + 1 + 15$

Add $1$ and $15$ .

$x^{2} - 10 x + 16$