-25x的平方y的平分 49-搜答案-智慧作业帮

把25拆成16+9(x²-8x+16)+(y²+6y+9)=0(x-4)²+(y+3)²=0平方大于等于0,相加等于0若有一个大于0,则另一个小于0,不成立.所

25x²-16y²=(5x+4y)(5x-4y)

（x-y)²=x²+y²-2xy=x²+y²+2xy-4xy=(x+y)²-4xy=7²-2[(x+y)²-x²

25x²+40x(y-x)+16(x-y)²25x²-40x(x-y)+16(x-y)²=[5x-4(x-y)]²=(x+4y)²

25(x-y)^2+10(y-x)+1=25(x-y)^2-10(x-y)+1={5(x-y)-1}^2=(5x-5y+1)^2

y=x-x^2与X轴围成的面积定积分得S=1/6所以直线,抛物线与X轴面积为s'=1/12直线与抛物线交点横坐标为1-k可求得(1/2X^2-1/3X^3)|1-k,0-k/2X^2|1-k,0=1/

25(x+y)的平方-9(x-y)的平方=[5(x+y)+3(x-y)][5(x+y)-3(x-y)]=(8x+2y)(2x+8y)=4(4x+y)(x+4y)

x^2(a-b)+y(b-a)=x^2(a-b)-y(a-b)=(a-b)(x^2-y)-49+36x^2y^2=36x^2y^2-49=(6xy-7)(6xy+7)64(a-b)^2-25(a+b)

x²+y²=25x-y=7两边平方得：x²+y²-2xy=492xy=25-49=-24xy=-12(x+y)²=x²+y²+2x

(x平方+y平方)平方-y平方=x平方+6所以（x²＋y²）²-（x²＋y²）-6=0（x²＋y²＋2）（x²＋y

x²+y²=25x+y=7(x+y)²=49x²+y²+2xy=492xy=49-25=24(x-y)²=(x+y)²-4xy=7

由x+y=25x+y=7则(x+y)=x+y+2xy=7=492xy=(x+y)-（x+y）=49-25=24则（x-y)=x+y-2xy=25-24=1因为：x＜y所以x-y＜0即x-y=-1

说明直线过圆心O(m/2,-1/2),带入得,m=-3

把x+y当做一个因子,7当做一个因子（x+y）^2-14(x+y)+49=（x+y）^2-2*7*(x+y)+7^2=(x+y-7)^2

36(x+y)²-49(x-y)²=[6(x+y)+7(x-y)][6(x+y)-7(x-y)]=(6x+6y+7x-7y)(6x+6y-7x+7y)=(13x-y)(-x+13y

解1题原式=[(x+y)/x]-[x/(x-y)]+[y²/(x²-xy)]=[(x+y)/x]-[x/(x-y)]+{y²/[x(x-y)]}={(x+y)(x-y)/

25x的平方-16y的平方=(5x+4y)(5x-4y)

x+y=7x-y=4解得,x=11/2,y=3/2或x+y=-7x-y=4解得,x=-3/2,y=11/2所以x²+y²=65/2再问：x+y=7怎么来的？请教一下谢谢再答：(x+

X²+25=y²y^2-x^2=25(y+x)(y-x)=25y+x=土25y-x=土1y=土13x=土12