Bài 6:
a: =>n+1=5
hay n=4
b: =>n-4=2
hay n=6
c: =>n+4=7
=>n=3
d: =>6-n=4
hay n=2
Bài 7:
a: =>x=6
b: \(\Leftrightarrow x^2=8+9+64=81\)
hay \(x\in\left\{9;-9\right\}\)
c: \(\Leftrightarrow x^3-x^2=0\)
\(\Leftrightarrow x^2\left(x-1\right)=0\)
hay \(x\in\left\{0;1\right\}\)