要具体步骤
16(x+2)的2次方=81
16(x+2)^2=81
(x+2)^2=81/16
(x+2)^2=(±9/4)^2
x+2=±9/4
x=1/4或x= -17/4
[4(x+2)]²=9²
x+2=±4.5
x=6.5,x=-2.5