1.
43²＋86x57＋57²
=43²＋2x43x57＋57²
=（43+57）^2
=10000
2.
4b-4ab+a²b
=b(4-4a+a^2)
=b(2-a)^2
3.已知x²-3x+1＝0,求x²+x的平方分之一.
x^2-3x+1=0
x^2+1=3x
x+ 1/x=3
x^2+1/x^2=(x+1/x)^2-2=7