1. π(13.4/2)^2-π(6.6/2)^2
=π(6.7^2-3.3^2)
=π(6.7-3.3)(6.7+3.3)
=34π
2. 32a(x的平方+2x)的平方-2a
=2a[16(x^2+2x)-1]
=2a(4x^2+8x-1)(4x^2+8x+1)
3.-x的n+4次方+81x的n次方(y-z)的平方
=x^n[81(y-z)^2-x^4]
=x^n[9(y-z)-x^2][9(y-z)+x^2]
4.(x-y)的平方-8(x-y-2)
=(x-y)^2-8(x-y)+16
=(x-y-4)^2
5.4(x-y)+z的四次方(y-x)
=(x-y)(4-z^4)
=(x-y)(2-z^2)(2+z^2)