Rút gon các bt sau 

A=\(\sqrt{12}\)+2\(\sqrt{27}\)-3\(\sqrt{48}\)

C=\(\sqrt{20a}\)+4\(\sqrt{45a}\)-2\(\sqrt{125a}\)với a≥0

giải phương trình:

a,x(x+3)-(2x-1).(x+30)=0

b,x(x-3)-5(x-3)=0

c,\(\dfrac{1}{x+1}+\dfrac{5}{x-2}=\dfrac{3x}{\left(x+1\right)\left(x-2\right)}\)

d,\(\dfrac{x-1}{x+1}+\dfrac{x+1}{x-1}=\dfrac{4-2x^2}{\left(1-x^2\right)}\)