(7x^12+8x^2-14x^10-16)-(7x^12-7x^10+17x^8)-(8x^2-7x^8)=7x^12+8x^2-14x^10-16-7x^12+7x^10+17x^10-17x^8-8x^2+7x^8=10x^10-10x^8-16