1) -7x²-(8x²+3x+6) = -7х²-8х²-3х-6 = -15х²-3х-6
2) 13(x²-4x+1)+(5x²+6x+1) = 13х²-52х+13+5х²+6х+1=18х²-46х+14
1) -7x²-(8x²+3x+6) = -7х²-8х²-3х-6 = -15х²-3х-6
2) 13(x²-4x+1)+(5x²+6x+1) = 13х²-52х+13+5х²+6х+1=18х²-46х+14