77. 1(x−1)2−1(x+1)21(x−1)2−1(x+1)2
79. −12(x−1)+x−12(x2+1)+1(x−1)2−12(x−1)+x−12(x2+1)+1(x−1)2
81. −4x+2−8(x+2)2−1(x+1)2+5x+1−4x+2−8(x+2)2−1(x+1)2+5x+1
83. 1+2x+1−1x+21+2x+1−1x+2