`#3107.101107`
2.
a.
`5^(x + 3) + 3*5^x = 3200`
`=> 5^x * 5^3 + 3*5^x = 3200`
`=> 5^x * (5^3 + 3) = 3200`
`=> 5^x * 128 = 3200`
`=> 5^x = 3200 \div 128`
`=> 5^x = 25`
`=> 5^x = 5^2`
`=> x = 2`
Vậy, `x = 2`
b.
`7^(2x + 1) + 5*7^(2x) = 588`
`=> 7^(2x) * 7 + 5*7^(2x) = 588`
`=> 7^(2x) * (7+5) = 588`
`=> 7^(2x) * 12 = 588`
`=> 7^(2x) = 588 \div 12`
`=> 7^(2x) = 49`
`=> 7^(2x) = 7^2`
`=> 2x = 2`
`=> x = 1`
Vậy, `x = 1`
c.
`121^(x + 1) + 11^(2x) = 14762`
`=> (11^2)^(x + 1) + 11^(2x) = 14762`
`=> 11^(2x + 2) + 11^(2x) = 14762`
`=> 11^(2x) * 121 + 11^(2x) = 14762`
`=> 11^(2x) * (121 + 1) = 14762`
`=> 11^(2x) * 122 = 14762`
`=> 11^(2x) = 14762 \div 122`
`=> 11^(2x) = 121`
`=> 11^(2x) = 11^2`
`=> 2x = 2`
`=> x = 1`
Vậy, `x = 1.`
