Answer
$3a^{2}-6a+11$
Work Step by Step
$(-a^{2}+1)-(a^{2}-3)+(5a^{2}-6a+7)$
Remove all the parentheses. To remove the second one, change the sign of every term inside it:
$-a^{2}+1-a^{2}+3+5a^{2}-6a+7=...$
Simplify by combining like terms:
$...=(-1-1+5)a^{2}-6a+(1+3+7)=...$
$...=3a^{2}-6a+11$
