已知xy=9，x≥y＞1，t=（log3x）（log3y）则（ ）
举一反三
- <img src="http://edu-image.nosdn.127.net/E6A0628104FCB0F521FBF2AAAC7F1968.png?imageView&thumbnail=890x0&quality=100" style="width: 558px; height: 33px;" />? syms xy=log(1/x*x+exp(x))+sin(1-x^2)dy/dx=diff(y,x)|syms xy=log(1/x/x+exp(x))+sin(1-x^2)dydx=diff(y,x)|syms xy=log(1/x/x+exp(x))+sin(1-x)^2dydx=diff(y,x)|syms xy=log(1/x/x+exp^x)+sin(1-x^2)dydx=diff(y,x)
- 求不定积分[img=115x46]17da65382f8e1b9.png[/img]； （ ） A: x - (5*log(x + 1))/4 - (3*log(x - 3)) B: (5*log(x + 1))/4 - (3*log(x - 3)) C: x - (5*log(x + 1))/4 - (3*log(x - 3))/4 D: (5*log(x + 1))/4 - (3*log(x - 3))/4
- 函数y=3x的反函数是（） A: y=(1/3)x(x＞0) B: -y=(1/3)x(x＞0) C: y=log3x(x＞0) D: -y=-log3x(x＞0)
- 用R程序编程求下列的值，正确的命令是 （ ）[img=273x30]180398c76b70239.png[/img] A: x<-log(2);y<-log(3);100^(2*x-y) B: x<-log10(2);y<-log10(3);100^(2*x-y) C: x<-log10(2);y<-log10(3);100^(2x-y) D: x<-log(2);y<-log(3);100^(2x-y)
- 设随机变量X,Y有D(X)= 9,D(Y)= 4,ρXY =1/3,则Cov(X,Y)=____