Question 273645
4x^2-20x+21=0

x^2-5x+21/4=0
x^2-5x=-21/4
(5/2)^2
25/4
25/4 to both sides
x^2-5x=-21/4
x^2-5x+25/4=1
(x-5/2)^2=1
|x-5/2|=1
+(x-5/2)=+1
x=2/2+5/2=7/2
x-5/2=-1
x-5/2=-1
x=3/2
x=7/2 and x=3/2

*[invoke change_this_name4450 4, -20, 21, "x"]