x + 1 : 0,75 = 1,4 : 0,25

<=> \(x+\dfrac{4}{3}=5,6\)

<=> \(x=\dfrac{64}{15}\)

Vì \(x=99\Rightarrow98=x-1\)

Thay \(98=x+1\)vào biểu thức A , ta có :

\(A=x^7-\left(x-1\right)x^6-\left(x-1\right)x^5-\left(x-1\right)x^4-\left(x-1\right)x^3-\left(x-1\right)x^2-\left(x-1\right)x+1\)

\(\Rightarrow A=x^7-x^7+x^6-x^6+x^5-x^5+x^4-x^4+x^3-x^3+x^2-x^2+x+1\)

\(\Rightarrow A=x+1=99+1=100\)

Tại x = 99

x=75x98+39=7389

x=75 x 98 + 39
x=       7389

x=75x98+39=7389

x=75*98+39=7389

x : 98 = 75 ( dư 39 )

       x = 75 x 98 + 39

       x = 7389

Ta có: (x -39):98=75

=>x-39=7350

=>x=7389

Vậy x=7389

x : 98 = 75 dư 39 

nên (x-39) : 98 = 75

    (x-39) = 75 x 98

    x - 39 = 7350

   x = 7350 + 39

  x = 7389