how do we solve: sqrt(x^2-10x+25)=4 ?
\(x^2-10x+25 = (x-5)^2\)
\(\begin{array}{rcll} \sqrt{x^2-10x+25} &=& 4 \\ \sqrt{(x-5)^2} &=& 4 \\ x-5 &=& 4\\ x &=& 4+5\\ x &=& 9 \end{array}\)
