Question 406473
x^2-13x+42=0  
  
squaring method

x^2-13x+169/4 +42=+169/4 

(x-13/2)^2= 169/4 -42

(x-13/2)^2= 1/4

Take the square root on both sides

(x-13/2) = +/- 1/2
..
x= 13/2 +1/2 = 7
OR

x=13/2 -1/2 =6