Step-by-step explanation:
[tex] \sqrt{28 - 6x} = x - 6 \\ ({ \sqrt{28 - 6x}) }^{2} = {(x - 6)}^{2} \\ + - (28 - 6x) = {x}^{2} - 12x + 36 \\ 0 = {x}^{2} - 6x + 8 \\ 0 = (x - 2)(x - 4) \\ x - 2 = 0 \\ x - 4 = 0 \\ x = 2 \\ x = 4 \\ we \: must \: check \: the \: answer \: \\ \sqrt{28 - 6(2)} = 2 - 6 \\ \sqrt{16} = - 4 \\ 4 = - 4 \\ it \: is \: wrong. \: \\ \sqrt{28 - 6(4)} = 4 - 6 \\ \sqrt{4} = - 2 \\ 2 = - 2 \\ it \: is \: wrong \: too.[/tex]
-( 28 - 6x ) = x² - 12x + 36
x² - 18x + 64 = 0
√∆ = √( 324 -256)= √68 = 2√17
x = (18 ± 2√17)/2 = 9 ± √17 → 9+√17 ✓
9-√17 is not acceptable because the radical answer can not be negative.
