xy132x4y42求xy是多少

赵政阅21752x+y=18 2y - x=21 求x和y分别是多少?求解过程 -
穆制泥13010833752 ______ 2y-x=21两边同乘以2得: 4y-2x=42 2x+y=18 两式相加得:4y+y=42+18 5y=60 y=12 x=3

赵政阅2175若X^+XY+Y=14,Y^+XY+X=28<求X+Y的值(过程及答案)
穆制泥13010833752 ______ 解:两式相加得出:X^+XY+Y+Y^+XY+X=14+28=42 前者为(x+y)^2+(x+y)=42 令x+y=a 则有a^2+a-42=0 所以a=-7或者a=6

赵政阅2175已知x+y=4,xy=1,试分别求出x² - y²+8y和x³y+xy³的值 -
穆制泥13010833752 ______ 1、x+y=4,可知y=4-x,带入x²-y²+8y,得:x²-(4-x)²+8(4-x)=16;2、x³y+xy³=xy(x²+y²)=xy(x²+2xy+y²-2xy)=xy((x+y)²-2xy)=xy(x+y)²-2x²y²=1X4-2X1²=2

赵政阅21754x十5y二520且5x十4y二533求xy分别是多少 -
穆制泥13010833752 ______ 4x+5y=520 (1)5x+4y=533 (2) (1)X5-(2)X49y=468 y=52 x=65

赵政阅2175x+y=78,3x+5y=318要求x.y各为多少 -
穆制泥13010833752 ______ x+y=78,3x+5y=318要求x.y各为多少 3x+3y=234,3x+5y=318 2y=84 y=42 x=36

赵政阅2175X加y等于64.2X加y等于124.X等于多少.y等于多少? -
穆制泥13010833752 ______ X加y等于64.则y为64-x.2x+64-x=124.由此解方程得:x=60,y=4.

赵政阅2175已知xy=3,x+y=4,求x2+y2 - 3xy的值 -
穆制泥13010833752 ______ ∵x+y=4,xy=3,∴x2+y2-3xy=(x+y)2-5xy=42-5*3=16-15=1.

赵政阅2175ax+by=3 ax2+by2=7 ax3+by3=16 ax4+by4=42 求:ax5+by5
穆制泥13010833752 ______ (ax2+by2)(x+y)=(ax3+by3)+(ax+by)xy (ax3+by3)(x+y)=(ax4+by4)+(ax2+by2)xy (ax4+by4)(x+y)=(ax5+by5)+(ax3+by3)xy ==> 7(x+y)=16+3xy 16(x+y)=42+7xy 42(x+y)=(ax5+by5)+16xy ===> ax5+by5 = 20

赵政阅2175已知正实数x,y满足xy+2x+3y=42,则xy+5x+4y的最小值为___. -
穆制泥13010833752 ______[答案] ∵正实数x,y满足xy+2x+3y=42,∴y=42-2x3+x>0,x>0,解得0

赵政阅2175已知x+y xy x4+y4 求x4 - y4 -
穆制泥13010833752 ______[答案] 设x+y=m(1) xy=n(2) x^4+y^4=p(3) 由(1)(x+y)²=m², x²+2xy+y²=m² x²+y²=m²-2n, (x²+y²)²=(m²-2n)² x^4+2x²y²+y^4=(m²-2n)² x^4+y^4=(m²-2n)²-2n² (x^4+y^4)²=[(m²-2n)²-2n²]² x^8+2x^4y^4+y^8=[(m²-2n)²-2n²]² ...