=4/151/201235
10.5
0.4x-0.8x=1 两边乘52x-4x=52(x-1)=7x-1=±√7/2=±1/2 √14x=1±1/2 √14
1/2x1/3+1/3x1/4+1/4x1/5+1/10x1/11 =(1/2- 1/3) + (1/3 -1/4) + + (1/10 - 1/11) =1/2 - 1/11 =9/22
(1-1/2)(1-1/3)(1-1/4)…(1-1/9)(1-1/10)=(1+1/2)(1-1/2)(1+1/3)(1-1/3)(1+1/4)(1-1/4)……(1+1/9)(1-1/9)(1+1/10)(1-1/10)=3/2x4/3x5/4x……x10/9x11/10x1/2x2/3x3/4x……x8/9x9/10=11/2x1/10=11/20
5X2x5.=30
0.8x一(50一x)x0.3=180.8x一15+0.3x=180.8x+0.3x=18+151.1x=33x=30
31*1/2*1/3 + 41*1/3*1/4 + 51*1/4*1/5=(30+1)*1/2*1/3 + (40+1)*1/3*1/4 + (50+1)*1/4*1/5=5+1/6 + 10/3+1/12 + 5/2+1/20=300/60 + 10/60 + 200/60 + 5/60 + 150/60 + 3/60=668/60=167/15
3x^2-10x+7=0解:x={-(-10)±√[(-10)^2-4*3*7]}/(2*3) =(5±2)/3 x=7/3,或x=1望采纳.请点击本页面中的“选为满意回答”按钮,谢谢!
1/5÷[ (2/3+1/5)x1/13]= 1/5÷[ (10+3)/15x1/13]= 1/5÷[ 13/15x1/13]=1/5÷1/15=1/5*15=3