A= 1+3\(^2\).(1+ 3\(^2\)+3\(^4\)+...+3\(^{64}\))

A= 1+9.(1+ 3\(^2\)+3\(^4\)+...+3\(^{64}\))

A= 10.(1+ 3\(^2\)+3\(^4\)+...+3\(^{64}\)) chia hết cho 10

Vậy A chia hết cho 10

x= -2002 nhan. Dùng máy tính cầm tay sẽ ra

\(\frac{x+1}{2001}+\frac{x+2}{200}=\frac{x+3}{1999}+\frac{x+4}{1998}\)

\(\left(\frac{x+1}{2001}+1\right)+\left(\frac{x+2}{2000}+1\right)=\left(\frac{x+3}{1999}+1\right)+\left(\frac{x+4}{1998}+1\right)\)

\(\frac{x+2002}{2001}+\frac{x+2002}{2000}=\frac{x+2002}{1999}+\frac{x+2002}{1998}\)

\(\frac{x+2002}{2001}+\frac{x+2002}{2000}-\frac{x+2002}{1999}-\frac{x+2002}{1998}=0\)

\(\left(x+2002\right).\left(\frac{1}{2001}+\frac{1}{2000}-\frac{1}{1999}-\frac{1}{1998}\right)=0\)

\(\Rightarrow x+2002=0\)

\(\Rightarrow x=0-2002\)

\(\Rightarrow x=-2002\)

x - 3 = x - 3

x -3 = 3-3

x - 3 = 0 

x = 0 + 3

x = 3

\(\Rightarrow x-3\in\left\{x-3;-x+3\right\}\)

+) x - 3 = x - 3 => x là bất kì số tự nhiên nào

+) x - 3 = -x + 3

    2x = 6

     x = 3

Vậy,.......

Học tốt nhé~

\(10A=10^2+10^3+...+10^{1000}\)

\(10A-A=\left(10^2+10^3+...+10^{1000}\right)-\left(10+10^2+...+10^{999}\right)\)

\(9A=10^{1000}-10\)

\(A=\frac{\left(10^{1000}-10\right)}{9}\)

Học tốt nhé~

\(A=10+10^2+10^3+...+10^{999}\)

\(\Rightarrow10A=10^2+10^3+10^4+...+10^{999}\)

\(\Rightarrow10A-A=(10^2+10^3+...+10^{999})-(10+10^2+...+10^{999})\)

\(\Rightarrow9A=10^{999}-10\)

\(\Rightarrow A=(10^{999}-10)\div9\)

thay a=1 ; b=9 ; c=8 vào biểu thức ta có 198=11.(1+9+8)

                                                            198=11. 18

                                                            198=198

phần b là 6+x nha các bạn. mình viết sai đề

\(\frac{15}{24}-\frac{3}{8}-\frac{1}{6}\)

\(=\frac{5}{8}-\frac{3}{8}-\frac{1}{6}\)

\(=\frac{3}{12}-\frac{2}{12}\)

\(=\frac{1}{12}\)

\(\frac{15}{24}-\frac{3}{8}-\frac{1}{6}\)

\(=\frac{5}{8}-\frac{3}{8}-\frac{1}{6}\)

\(=\frac{2}{8}-\frac{1}{6}\)

\(=\frac{12}{48}-\frac{8}{48}\)

\(=\frac{4}{48}=\frac{1}{12}\)

=\(18.\left(\frac{-5}{6}\right)^2-2.\frac{1}{4}.\frac{-4}{5}+2\)

\(=18.\frac{25}{36}+\frac{2}{5}+2\)

\(=\frac{25}{2}+\frac{12}{5}=\frac{149}{10}\)

Linh ơi tự làm đi nhá, ai cho gian lận ntn