-
-
墙上一颗钉
丨Lv 3
1.C1/z=1/(-3-4i)=(-3 4i)/[(-3-4i)(-3 4i)]=(-3 4i)/25虚部:4/252.Da⊥b,a*b=0,即3*4-3x=0,x=43.A点坐标(4,0),B点坐标(0,3)OA=4,OB=3,AB=5,周长:3 4 5=124.球表面积4πR2=4π小圆的面积:4π/6=2π/3又小圆面积=πr^2,所以2π/3=πr^2,得r^2=2/3球心到小圆的距离=√(R^2-r^2)=√(1-2/3)=√3/35.Tr 1=C(6,r)x^[2(6-r)]*(1/x)^r=C(6,r)x^(12-3r)令12-3r=0得r=4,即为常数项C(6,4)=15