B=4 + 4^2 + 4^3 + 4^4 + ..... + 4^2001
4B=4^2 + 4^3 + 4^4 + ..... + 4^2002
4B-B=(4^2 + 4^3 + 4^4 + ..... + 4^2002)-(4 + 4^2 + 4^3 + 4^4 + ..... + 4^2001)
3B=4^2002-4
B=(4^2002-4)/3

ờ quên a= 0 nhìn lộn đề

a)=\(\dfrac{3}{8}+\dfrac{3}{8}=\dfrac{3}{4}\)

b)=\(\dfrac{-5}{12}+\dfrac{17}{11}=\dfrac{149}{132}\)

\(\dfrac{5}{3}+\left(\dfrac{7}{17}+\dfrac{5}{11}+\dfrac{5}{12}\right)=\dfrac{5}{3}+\dfrac{2879}{2244}=2,9496\)

a) 3x(1-4y)

b)(3x-2)(3x+2)

c)(x-2)^2

d)x(4x+2)

\((2-x)(3x+1)-(2-x)(x+3)=0\)

<=>-4(x-2)(x+1)=0

=>x=2 hoac x=-1

\(x^3-3x^2+2=x^3-x^2-2x^2+2x-2x+2\)

\(=x^2(x-1)-2x(x-1)-2(x-1)\)

\(=(x^2-2x-2)(x-1)\)