Verified answer

1) ...= x^2-24x+144+24x= x^2+144

2) ... = x^2+16x+64 -x^2 -5x= 11x +64

3) ...= 2x^2 +4x -x^2 +4x -4= x^2 8x -4

4) ...= y^2 +14y+49 +y^2 +2y -7y -14= 2y^2 +9y +35

5) ...= a^2 -1 -a^2-8a-16= -8a-17

6) ...= 9x-x^2-90+10x+x^2+20x+100= 39x+10