7y-搜答案-搜狗做题网

代数式4y²-2y+5=7,那么代数式2y²-y+1=2∵4y²-2y+5=7∴4y²-2y=22(2y²-y)=22y²-y=1∴2y&#

(3x+y)(3x-7y)

(3x+y)(3x-y)=9x²-3xy+3xy-y²=9x²-y²

y平方+y+7(y平方+y)-9*2=8y²+8y-18=4(2y²+2y-9)是不是题错了感觉应该是：（y平方+y）²+7(y平方+y)-9*2=（y平方+y+9）（y

2(y-x)²-7(x-y)+6(x-y)-3(y-x)²=-(y-x)²-(x-y)=-(x-y)²-(x-y)=-(x-y)[(x-y)+1]=(y-x)(

5y^2+8y-489=0△=8^2-4*5*（-489）=9844质因数有4,23,107∴y=【-8土√△】/（2*10）即y1=【-4+√2461】/10y2=【-4-√2461】/10PS：一

(y^2+2y)^2-7(y^2+2y)-8

把y^2+2y看作整体=（y^2+2y-8）（y^2+2y+1)=（y+4)(y-2)(y+1)(y+1)

5y(8-y)-3y(5-3y)+2y(7-2y)>-3940y-5y²-15y+9y²+14y-4y²＞-3939y＞-39y＞-1

y-7-8y=2y-3-5y 咋写?

y=-1.

3(X-Y)²-4(X-Y)+7(X-Y)-6(X-Y)²=(3-6)(X-Y)²+(-4+7)(X-Y)=-3(X-Y)²+3(X-Y)

11y-12-2y²=y²-7y+10-(3y²-7)18y=12+10+7=39y=39/18

请问7y+2y等于几

这个问题的答案：9y

第一题：（x-y)/13=y/713y=7x-7y20y=7xx/y=20/7两边都加1（x+y)/y=27/7第二题：x/6=y/4=z/3（x,y,z,不为零）用特值法令x/6=y/4=z/3=1

(x-y)^2+7(x+y)-11(x-y)^2-8(x+y),=-10(x-y)²-(x+y)当x+y=-3,x-y=-1时=-10*(-1)²-(-3)=-10+3=-7

(7x+y)(7x-y)-(-x+y)(x-y)=(49x²-y²)-(-x²+2xy-y²)=49x²-y²+x²-2xy+y&

x=-2.5y=-3再问：过程再答：2x+y/3-2y=0①2(2x+y)-5=7y②展开②式，4x+2y-5=7y，移项整理的得4x-5y=5③将①整理得2x-5y/3=0④将④×2得4x-10y/

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!

(-3x+7y)(-7y-3x)-(x-3y)(2x+3y)=(3x-7y)(3x+7y)+(3y-x)(3y+2x)后半部分相当于(x+a)(x+b)=x^2+(a+b)x+ab=9x^2-49y^

(x-y)(3x-7y)²-4(x-y)(x+y)²=(x-y)[(3x-7y)²-4(x+y)²]=(x-y)(3x-7y-2x-2y)(3x-7y+2x+2

10y+2(7y-2)=5(4y+3)+3y10y+14y-4=20y+15+3y10y+14y-20y-3y=15+4y=19

因式分解2y^2+5y-7

2y^2+5y-7=（2y+7)(y-1)