a) `2 xx 3^x = 10 xx 3^12 + 8 xx 27^4`
`2 xx 3^x = 10 xx 3^12 + 8 xx (3^3)^4`
`2 xx 3^x = 10 xx 3^12 + 8 xx 3^12` `(``(x^a)^b = x^(axxb)` nhé pạn`)`
`2 xx 3^x = 3^12 xx (10 + 8)`
`2 xx 3^x = 3^12 xx 18`
`3^x : 3^12 = 18 : 2`
`3^(x - 12) = 9`
`3^(x - 12) = 3^2`
`-> x - 12 = 2`
`x = 2 + 12`
`x = 14`
b) `(19x + 2 xx 5^2) : 14 = (13 - 8)^2 - 4^2`
`(19x + 2 xx 5^2) : 14 = 5^2 - 4^2`
`(19x + 2 xx 25) : 14 = 25 - 16`
`(19x + 50) : 14 = 9`
`19x + 50 = 9 xx 14`
`19x + 50 = 126`
`19x = 126 - 50`
`19x = 76`
`x = 76 : 19`
`x = 4`
