45

so chia ba la so co tong chia het cho ba

=> 3246 (3+2+4+6 chia het cho 3)

=> 3546 (3+2+4+6 chia het cho 3)

=> 3846 (3+8+4+6 chia het cho 3)

hóng thôi chứ bt lm đâu

bn xem đề có thiếu xy // x'y' ko

\(\dfrac{1}{3}\)

\(=>2\left(x-1\right)+6=1\)

\(2\left(x-1\right)=-5\)

\(x-1=\dfrac{-5}{2}\)

\(x=\dfrac{-3}{2}\)

a)

\(=>2^{4x-8}=2^4\)

\(=>4x-8=4\)

\(4x=12\)

\(x=3\)

b)

\(=>2.\left(x.1\right)+6=1\)

\(2x\left(x.1\right)=-5\)

\(x.1=\dfrac{-5}{2}\)

\(x=\dfrac{-5}{2}\)

c)

\(7x.14=\dfrac{49}{2}\)

\(7x=\dfrac{7}{4}\)

\(x=\dfrac{1}{4}\)

12:5=2(du 2)

18:4=4(du 2)

23:4=5(du 3)

a) \(=x^3-3.x^2.2+3.x.2^2-2^3\)

\(=\left(x-2\right)^3\)

b)

\(=\left(-2x\right)^3+3.\left(-2x\right)^2.1+3.\left(-2x\right).1^2+1^3\)

\(=\left(-2x+1\right)^3\)

c)

\(=x^3-3.x^2.\dfrac{1}{2}y+3.x.\left(\dfrac{1}{2}y\right)^2-\left(\dfrac{1}{2}y\right)^3\)

\(=\left(x-\dfrac{1}{2}y\right)^3\)

d)

\(=\left(x-y\right)^3+3.\left(x-y\right)^2.2+3.\left(x-y\right).2^2+2^3\)

\(=\left[\left(x-y\right)+2\right]^3\)

\(=>\dfrac{4}{9}x+\dfrac{1}{2}=\dfrac{1}{5}\)

\(\dfrac{4}{9}x=\dfrac{1}{5}-\dfrac{1}{2}\)

\(\dfrac{4}{9}x=\dfrac{-3}{10}\)

\(x=\dfrac{27}{40}\)

hay \(\dfrac{4}{9}x+\dfrac{1}{2}=\dfrac{-1}{5}=>\dfrac{-63}{40}\)