含x^2与x项的系数之和分别为：a-2,b-2a
a-2=0 a=2
b-2a=0 b=2a=4
2.4x^2+20xy+25y^2=0
(2x+5y)^2=0
2x+5y=0
x=-3
-6+5y=0 y=6/5
(2x-5y)^2=(-6-6)^2=144
3.
4x^2+1+kx是关于x的完全平方式
4x^2+1+kx=(2x±1)^2=4x^2+1±4x k=±4
4.[(x^2+x)/x]-2x=x+1-2x=1-x
5.1/4a^2+ab+b^2=(b+1/2a)^2
周长：4*(b+1/2a)^2
6.a-b=b-c=3/5 a-c=6/5
(a-b)^2+(a-c)^2+(b-c)^2=2(a^2+b^2+c^2)-2(ab+ac+cb)=54/25
ab+ac+cb=[2-54/25]/2=-2/25
7.1/2x^2+2xy+2y^2=(√2/2x+√2y)^2
8.a^2+b^2+4a-6b+13=0
(a+2)^2+(b-3)^2=0
a+2=0 a=-2
b-3=0 b=3
a^2+b^3=4+27=31
9.1.5×10^6*3.0×10^5/(1.5×10^5)^2=20