x^2 y - 2 x y = ________；1 - x + 1/4 x^2 = __________；a^4 - 2a^2 + 1 =_______；（ a - b ）^2 - 4 =_______.

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x^2 y - 2 x y = ________；1 - x + 1/4 x^2 = __________；a^4 - 2a^2 + 1 =_______；（ a - b ）^2 - 4 =_______.

x^2 y - 2 x y = ________；1 - x + 1/4 x^2 = __________；a^4 - 2a^2 + 1 =_______；（ a - b ）^2 - 4 =_______.
x^2 y - 2 x y = ________；
1 - x + 1/4 x^2 = __________；
a^4 - 2a^2 + 1 =_______；
（ a - b ）^2 - 4 =_______.

x^2 y - 2 x y = ________；1 - x + 1/4 x^2 = __________；a^4 - 2a^2 + 1 =_______；（ a - b ）^2 - 4 =_______.
x^2 y - 2 x y =xy（x-2）
1 - x + 1/4 x^2 =（1-1/2x）^2
a^4 - 2a^2 + 1 =(a^2-1)^2
（ a - b ）^2 - 4 =(a-b+2)(a-b-2)

x²y-2xy=xy(x-2)
1-x+1/4x²=1²-2×1×(1/2x)+(1/2x)²=(1-1/2x)²
a^4-2a²+1=(a²)²-2×a²+1²=(a²-1)²=[(a+1)(a-1)]²=(a+1)²(a-1)²
(a-b)²-4=[(a-b)+2][(a-b)-2]=(a-b+2)(a-b-2)

填空 (x^2-y^2)(x+y)^2=(x-y)(____)^3 (5x-____)^2=____-10xy+y^2 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 已知x ^2+9y ^2-2x+12y+5=0,则x=____,y=____. 已知（2x+5y-4）+|x+5y-7|=0,则x=____,y=____. (5)若x/2=y/3(y不为0）则x/y=____,x+y/y=___,y/x-y=___. 若x,y互为相反数（y≠0）,则2x+5+2y+3x/y=____ 若实数x,y满足(x-2y-2)(3x+2y+2)+2(x2+4)=0,则x=____,y=____ 若实数x、y满足x^2+y^2+2xy+x-y=0,则x（max）=____,y（min）=____. 已知x为实数,y是纯虚数,且满足(2x-1)+(3-y)i=y-i,则x=____,y=____ 若x^2-4y^2=-15,2y-x=5,则x+2y=____ 已知x^2+y^2-4x+2y+5=0则x^y=____ 已知方程组3x-2y=5 4x+9y=2,则x+y=____ 已知2x+3y=2,9y,比4x大一,则x=___,y=____ 若|x-2y+1|+(x+2y-3)²=0,则x=___,y=____, 【数学提问】已知2x+y=7,x+2y=8,那么x-y=____. 若x^2-y^2=20,且x+y=-5,则x-y的值是____ x^2+4y^2-4x+20y+8=0,求x+y=____.