y等于x
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![y等于x](/uploads/image/f/920020-4-0.jpg?t=y%E7%AD%89%E4%BA%8Ex)
x/(y-x)
cosxcosy-sinxsiny
题在哪
(x-y)的四次方(x-y)-2(x-y)²(y-x)³=(x-y)的五次方+2(x-y)五次方=3倍(x-y)五次方
(x-y)³(x-y)²(y-x)=-(x-y)³(x-y)²(x-y)=-(x-y)³+2+1=-(x-y)^6
y=19.8-15.84=3.96x=y除以19.8=0.2
只是习惯上的代表而已.例如,若0°<A<180°,则sin(A±2лX)>0,为正;若180°<A<360°,则sin(A±2лX)<0,为负.
差不多,但是有小区别.arctan(x/y)的范围是(-π/2,π/2)而arctan(x,y)的范围是(-π,π]http://www.cplusplus.com/reference/clibrar
2x+y=6x+3y+|3x-y|=19如果3x-y>=0则方程为2x+y=64x+2y=19方程无解如果3x-y
若(x-y)/(x+y)=3那么x-y=3(x+y)x-y=3x+3y故x=-2y所以(x+2y)/(6x-7y)=(-2y+2y)/(6*(-2y)-7y)=0如果不懂,请Hi我,祝学习愉快!
x^2+y^2=(x+y)^2-2xy=(x+y)^2-2((x+y)^2-(x-y)^2)/4=1-2×(1-49)/4=25
x+y=19x-y=8.6两式相加2x=27.6x=13.8y=5.2
X+y=55X-y=13X=3y=5再答:点错了y=2
∵2(x+y)²-3x-3y-2=02(x+y)²-3(x+y)-2=0[(2(x+y)+1][(x+y)-2]=02(x+y)=-1或(x+y)=2即:x+y=-1/2或x+y=
中间的是X还是乘号再问:乘再问:我知道怎么做再问:就是想试试再答:(x+y)(x-y)=x^2-y^2(平方差公式)再问:恩再问:谢谢了再问:等半期考试回快点哈再答:请给好评再问:怎么给好评再答:点击
(x-y)(x+y)+(x-y)(x+y)=2*(x-y)(x+y)=2(x^2-y^2)=2x^2-2y^2
两式相加,得5x+5y=90因此3x+3y=54又3x+2y=44,y=102x+3y=46x=8