1)(y²+3y)/4·y/(2y+6)=(y³+3y²)/(8y+24);
6·x⁻⁵·y⁷·2.5·x⁷·y⁻⁶ =15x⁻⁵⁺⁷y⁷⁻⁶=15x²y;
2)2⁻³·2²/2⁻⁷=2⁻³⁺²⁺⁷=2⁶;
(-√13)²=13;
3)[(b+1)/(b-1)-b/(b+1)]:(3b+1)/(2b-2)=
=[(b+1)²-b(b-1)]/(b²-1):(3b+1)/2(b-1)=
=(b²+2b+1-b²+1)·2(b-1)/[b²-1)·(3b+1)]=2(b+1)·2(b-1)/(b²-1)(3b+1)=
=4/(3b-1);
(√6+√3)·√12-2√6·√3=√(6·12)+√(3·12)-2√(6·3)=
=6√2+6-2·3√2=6;