首先你表达的不太清楚,我理解为下面的算式,那里不对提出,
1,原式=a√(1/a)-1/a*√4a^3-a^2*4/√a^3=√a-2√a-4√a=-5√a,
当a=1.21时,原式=-5√1.21=-5*1.1=-5.5
2,a√(3/a)+3√a/3+√27a=√3a+√3a+3√3a=5√3a=15,则a=√3,
3,5√2-x=0.2√2+0.8√2=√2,x=4 √2,
4,√12-√1/18-(√72-√27)=2√3-(1/6)*√2-6√2+3√3=5√3-(37/36)*√2
=5a-(37/36)*b
5,3√(2/3)-(2/3)*√54+(3/2)√(8/3)=√6-2√6+√6=0,
6,读不懂式量
7,-2(x+3)^2≥0,得(x+3)^2 ≤0,∴x=-3,
8,要使原式有意义,x+2≥0且x+1≠0,即x≥-2且x≠-1.