初二数学题关于乘法公式2道1.x2+y2=25,x+y=7,且x大于y,求x-y的值2.已知x2+y2-6x+10y+34=0,求x+y的值 不光要答案,还要具体的过程,好的再加
2019-06-21
初二数学题关于乘法公式2道
1.x2+y2=25,x+y=7,且x大于y,求x-y的值2.已知x2+y2-6x+10y+34=0,求x+y的值 不光要答案,还要具体的过程,好的再加
优质解答
1.(x+y)^2=49 xy=12 (x-y)^2=x^2+y^2-2xy=25-24=1 x-y=1(x>y)
2.(x-3)^2+(y+5)^2-9-25+34=0 .(x-3)^2+(y+5)^2=0 .(x-3)^2=0且(y+5)^2=0 X=3 Y=-5
X+Y=-2
1.(x+y)^2=49 xy=12 (x-y)^2=x^2+y^2-2xy=25-24=1 x-y=1(x>y)
2.(x-3)^2+(y+5)^2-9-25+34=0 .(x-3)^2+(y+5)^2=0 .(x-3)^2=0且(y+5)^2=0 X=3 Y=-5
X+Y=-2