Question

Answer 1

Câu 6:

a: \(x\in\left\{42;63\right\}\)

b: \(x\in\left\{15;30\right\}\)

Answer 2

Bài 5:

\(M=1+3+\left(3^2+3^3+3^4\right)...+\left(3^{98}+3^{99}+3^{100}\right)\\ M=4+\left(1+3+3^2\right)\left(3^2+...+3^{98}\right)\\ M=4+13\cdot\left(3^2+...+3^{98}\right):13\left(dư\text{ 4}\right)\)

\(M=1+\left(3+3^2+3^3+3^4\right)+...+\left(3^{97}+3^{98}+3^{99}+3^{100}\right)\\ M=1+\left(1+3+3^2+3^3\right)\left(3+...+3^{97}\right)\\ M=1+40\left(3+...+3^{97}\right):40\left(dư\text{ 1}\right)\)