1.-7x²+10x+12-(4x²-5x-6)
=-7x²-4x²+10x+5x+12-6
=-11x²+15x+6
-11x²+15x+6+(4x²-5x-6)
=-11x²+15x+6+4x²-5x-6
=-11x²+4x²+15x-5x+6-6
=-7x²+10x
1.-7x²+10x+12-(4x²-5x-6)
=-7x²-4x²+10x+5x+12-6
=-11x²+15x+6
-11x²+15x+6+(4x²-5x-6)
=-11x²+15x+6+4x²-5x-6
=-11x²+4x²+15x-5x+6-6
=-7x²+10x