a)\(\left(4-3n\right)^2=121\)
\(\left(4-3n\right)^2=11^2=\left(-11\right)^2\)
\(\Rightarrow4-3n=11\)và \(4-3n=-11\)
TH1: Nếu 4 - 3n = 11
\(3n=4-11\)
\(3n=-7\)
\(n=-\frac{7}{3}\)
TH2: Nếu 4 - 3n = -11
\(3n=4-\left(-11\right)\)
\(3n=15\)
\(n=15:3\)
\(n=5\)