x-開方x-12 = 0
x-12 = 開方x
(x-12)^2 = x
x^2-24x+144 = x
x^2-25x+144 = 0
(x-9)(x-16) = 0
x=9 或 x=16
代9:左方:9-開方9-12 代9:左方:9-開方9-12
=9-(3)-12 =9-(-3)-12
=-6 =9+3-12
左方不等於右方 =0
代16:左方:16-開方16-12 左方等於右方
=16-4-12 代16:左方:16-開方16-12
=0 =16-(-4)-12
左方等於右方 =16+4-12
=8
左方不等於右方
x=9(捨去) 或 x=16 x=9 或 x=16(捨去)
咁究竟左岩定右岩???
因為開方9=3/-3,開方16=4/-4