3n²-n(4n-6m) = 3n²-4n²+6mn = -1n²+6mn;
5a+2a(3a+5) = 5a+6a²+10a = 15a+6a²;
a(a+b)-b(a-b) = a²+ab-ab+b² = a²+b²;
2x(x-y)-y(y-2x) = 2x²-2xy-y²+2xy = 2x²-y²;
2p(1-p-3p²)-3p(2-p-2p²) = 2p-2p²-6p³-6p+3p²+6p² = -4p+p²-3p³;
2c(5a-3c²)-c(a-6c²)+3a(9a-c) = 10ac-6c³-ac+6c³+27a²-3ac = 6ac+27a²;
с(2а+b) = 2ac+cb.