若有理数x,y满足|x|=7,|y|=4,且|x+y|=x+y,则x-y=( )
A: 11
B: 3
C: 3或11
D: -3
A: 11
B: 3
C: 3或11
D: -3
举一反三
- 若|x|=3,|y|=4,且x>y,则x+y=______.
- [(x-y)^3×(√x+√y)^(-3)+3(x√y-y√x)]/(x√x+y√y)
- x+y=8()x-y=4()求x和y各等于几?A.()x=6()y=2()B.()x=5()y=3()C.()x=7()y=1()D.()x=3()y=5
- 有程序段:x:=7;y:=3;x:=x+y;y:=x-y;x:=x-y,执行后,变量x的值是() A: 7 B: 3 C: 10 D: 4
- 绘制函数 z=(x+y)^2 的曲面图 A: x=-3:0.1:3; y=-3:0.1:3; z=(x+y)^2; surf(x,y,z) B: x=-3:0.1:3; y=-3:0.1:3; z=(x+y).^2; surf(x,y,z) C: x=-3:0.1:3; y=-3:0.1:3; z=(x+y).^2; meshgrid(x,y,z); surf(x,y,z) D: x=-3:0.1:3; y=-3:0.1:3; [X,Y]=meshgrid(x,y); Z=(X+Y).^2; surf(X,Y,Z)