RÚT GỌN BIỂU THỨC SAU:
a, 2x(x+3)-2(x+2)²
b, 2(x+2)(x-2)-(2x-3)(x-1)
c,(x+1)²-2(x²+6)-(x+1)(x-1)
d,(2x+1)²(2x+1)(x-1)+(x-1)²
e, 15xy²/27x²y
f,4xy³(x-2y)/12x²y(2y-x)²
g,20x-45/4x²+12x+9
h,(x-5)²-9/x²-4x+4
i,x40 +x^30+x^20+x^10+1/x^45+x^40+x^30+...+x^5+1