Đáp án:+Giải thích các bước giải:
13) `6x + x = 5^11 : 5^9 + 3^1`
`x . ( 6 + 1 ) = 5^2 + 3`
`x . 7 = 28`
`x = 28 : 7`
`x = 4`
14) `7x - x = 5^21 : 5^19 + 3 . 2^2 - 7^0`
`x . ( 7 - 1 ) = 5^2 + 3 . 4 - 1`
`x . 6 = 25 + 12 - 1`
`x . 6 = 36`
`x = 36 : 6`
`x = 6`
15) `7x - 2x = 6^17 : 6^15 + 44 : 11`
`x . ( 7 - 2 ) = 6^2 + 4`
`x . 5 = 36 + 4`
`x . 5 = 40`
`x = 40 : 5`
`x = 8`
16) `3^x = 9`
`3^x = 3^2`
→ `x = 2`
17) `4^x = 64`
`4^x = 4^3`
→ `x = 3`
18) `9^(x-1) = 9`
→ `x - 1 = 0`
→ `x = 0 + 1`
→ `x = 1`
19) `x^4 = 16`
→ `x^4 = 2^4`
→ `x = 2`
20) `2^x : 2^5 = 1`
`2^x = 1 . 2^5`
`2^x = 2^5`
→ `x = 5`
