x^2-8x+16=1\\ \\x^2-8x+16-1=0\\ \\x^2-8x+15=0\\ \\\Delta = b^{2}-4ac = (-8)^{2}-4*1*15=64-60=4 \\ \\x_{1}=\frac{-b-\sqrt{\Delta }}{2a} =\frac{8- \sqrt{4}}{2}=\frac{8-2}{2}= \frac{6}{2}=3\\ \\x_{2}=\frac{-b+\sqrt{\Delta }}{2a} =\frac{8+ \sqrt{4}}{2}=\frac{8+2}{2}= \frac{10}{2}=5\\ \\Answer : x=3 \ \ or \ \ x = 5
