Даю больше 30 баллов !!!
1. 3m+n-m²=3*4+2-4²=12+2-16=-2 2. 9x²-24xy+16y²=9*(2 1/3)²-24*(2 1/3)*(1 3/4)+16*(1 3/4)²=9*(7/3)²-24*(7/3)*(7/4)+16*(7/4)²=9*(49/9)-24*(49/12)+16*(49/16)=49-98+49=0 3. m³+n³-mn=3³+2³-3*2=27+8-6=29 4. x/(x+y)=√2/(√2+√8)=√2/(√2+2√2)=√2/3√2=1/3