cl+dg53+xy
@亓中1179：设lg2=x,lg5=y,化简:(x+y)(x^2 - xy+y^2)+3xy. -
柏陆13353142914…… 因为lg2+lg5=lg(2*5)=lg10=1,且lg2=x,lg5=y,所以x+y=1,所以(x+y)(x^2-xy+y^2)+3xy=(x+y)[(x+y)^2-3xy]+3xy=1*(1^2-3xy)+3xy=1-3xy+3xy=1.
@亓中1179：y=sinxy+cos(x+y)求y对x的偏导数 - 作业帮
柏陆13353142914…… [答案] y`=cosxy(y+xy`)-sin(x+y)(1+y`) =ycosxy+xy`cosxy-sin(x+y) -y`sin(x+y) y`-xy`cosxy+y`sin(x+y)=ycosxy-sin(x+y) y`=[ycosxy-sin(x+y)]/[1-xcosxy+sin(x+y)]
@亓中1179：x+y=6,xy=8,求5x+xy+5y/x - xy+y的值 - 作业帮
柏陆13353142914…… [答案] 5x+xy+5y/x-xy+y =[5(x+y)+xy]/[(x+y)-xu] =(5*6+8)/(6-8) =-19
@亓中1179：计算 (根号下x+xy - 根号下xy)(根号下y+y的平方+y)(x>0 y>0) 快啊. - 作业帮
柏陆13353142914…… [答案] [√(x+xy)-√(xy)][√(y+y²)+y] =√x[√(1+y)-√y]√y[√(1+y)+√y] =√(xy)(1+y-y) =√(xy)
@亓中1179：xy+5y+[5x - (3xy+y+x)]等于多少 -
柏陆13353142914…… xy+5y+[5x-(3xy+y+x)]=xy+5y+[5x-3xy-y-x]=xy+5y+5x-3xy-y-x=-2xy+4y+4x
@亓中1179：已知a=2x2+3xy - 1 b= - x2+xy+2x - 1如果2A+3B中不含x的一次项 求y -
柏陆13353142914…… a=2x²+3xy-1 b=-x²+xy+2x-12A+3B=2(2x²+3xy-1)+3(-x²+xy+2x-1)=4x²+6xy-2-3x²+3xy+6x-3=x²+9xy+6x-5=x²+(9y+6)x-5 不含x的一次项 所以9y+6=0 y=-2/3 如果您认可我的回答,请点击“采纳为满意答案”,祝学习进步!
@亓中1179：已知x=a+b/a - b,y=a - b/a+b,且19x的平方+143xy+19y的平方=2005则x+y=? -
柏陆13353142914…… x=(a+b)/(a-b),y=(a-b)/(a+b),xy=(a+b)/(a-b)*(a-b)/(a+b)=119x^2+143xy+19y^2=200519(x+y)^2+105xy=200519(x+y)^2+105=200519(x+y)^2=1900(x+y)^2=100(x+y)=±10
@亓中1179：(x+y)^3 - x^3 - y^3+3xy因式分解 - 作业帮
柏陆13353142914…… [答案] (x+y)^3-x^3-y^3+3xy =(x+y)^3-(x+y)(x²-xy+y²)+3xy =(x+y)(x²+2xy+y²-x²+xy-y²)+3xy =3xy(x+y)+3xy =3xy(x+y+1)
@亓中1179：分解因式:(xy+1)(x+1)(y+1)+xy - 作业帮
柏陆13353142914…… [答案] (xy+1)(x+1)(y+1)+xy =(xy+1)(xy+x+y+1)+xy =(xy+1)[(xy+1)+x+y]+xy =(xy+1)^2+x(xy+1)+y(xy+1)+xy =(xy+1+x)(xy+1+y)
@亓中1179：若x+y=5,xy=6,则x2y+xy2的值为______. - 作业帮
柏陆13353142914…… [答案] ∵x+y=5,xy=6, ∴x2y+xy2 =xy(x+y) =5*6 =30. 故答案为:30.
柏陆13353142914…… 因为lg2+lg5=lg(2*5)=lg10=1,且lg2=x,lg5=y,所以x+y=1,所以(x+y)(x^2-xy+y^2)+3xy=(x+y)[(x+y)^2-3xy]+3xy=1*(1^2-3xy)+3xy=1-3xy+3xy=1.
@亓中1179：y=sinxy+cos(x+y)求y对x的偏导数 - 作业帮
柏陆13353142914…… [答案] y`=cosxy(y+xy`)-sin(x+y)(1+y`) =ycosxy+xy`cosxy-sin(x+y) -y`sin(x+y) y`-xy`cosxy+y`sin(x+y)=ycosxy-sin(x+y) y`=[ycosxy-sin(x+y)]/[1-xcosxy+sin(x+y)]
@亓中1179：x+y=6,xy=8,求5x+xy+5y/x - xy+y的值 - 作业帮
柏陆13353142914…… [答案] 5x+xy+5y/x-xy+y =[5(x+y)+xy]/[(x+y)-xu] =(5*6+8)/(6-8) =-19
@亓中1179：计算 (根号下x+xy - 根号下xy)(根号下y+y的平方+y)(x>0 y>0) 快啊. - 作业帮
柏陆13353142914…… [答案] [√(x+xy)-√(xy)][√(y+y²)+y] =√x[√(1+y)-√y]√y[√(1+y)+√y] =√(xy)(1+y-y) =√(xy)
@亓中1179：xy+5y+[5x - (3xy+y+x)]等于多少 -
柏陆13353142914…… xy+5y+[5x-(3xy+y+x)]=xy+5y+[5x-3xy-y-x]=xy+5y+5x-3xy-y-x=-2xy+4y+4x
@亓中1179：已知a=2x2+3xy - 1 b= - x2+xy+2x - 1如果2A+3B中不含x的一次项 求y -
柏陆13353142914…… a=2x²+3xy-1 b=-x²+xy+2x-12A+3B=2(2x²+3xy-1)+3(-x²+xy+2x-1)=4x²+6xy-2-3x²+3xy+6x-3=x²+9xy+6x-5=x²+(9y+6)x-5 不含x的一次项 所以9y+6=0 y=-2/3 如果您认可我的回答,请点击“采纳为满意答案”,祝学习进步!
@亓中1179：已知x=a+b/a - b,y=a - b/a+b,且19x的平方+143xy+19y的平方=2005则x+y=? -
柏陆13353142914…… x=(a+b)/(a-b),y=(a-b)/(a+b),xy=(a+b)/(a-b)*(a-b)/(a+b)=119x^2+143xy+19y^2=200519(x+y)^2+105xy=200519(x+y)^2+105=200519(x+y)^2=1900(x+y)^2=100(x+y)=±10
@亓中1179：(x+y)^3 - x^3 - y^3+3xy因式分解 - 作业帮
柏陆13353142914…… [答案] (x+y)^3-x^3-y^3+3xy =(x+y)^3-(x+y)(x²-xy+y²)+3xy =(x+y)(x²+2xy+y²-x²+xy-y²)+3xy =3xy(x+y)+3xy =3xy(x+y+1)
@亓中1179：分解因式:(xy+1)(x+1)(y+1)+xy - 作业帮
柏陆13353142914…… [答案] (xy+1)(x+1)(y+1)+xy =(xy+1)(xy+x+y+1)+xy =(xy+1)[(xy+1)+x+y]+xy =(xy+1)^2+x(xy+1)+y(xy+1)+xy =(xy+1+x)(xy+1+y)
@亓中1179：若x+y=5,xy=6,则x2y+xy2的值为______. - 作业帮
柏陆13353142914…… [答案] ∵x+y=5,xy=6, ∴x2y+xy2 =xy(x+y) =5*6 =30. 故答案为:30.
