Question 93105
x^2 - 6x - 40+40 =40
x^2-6x=40
{{{(x^2-6x+(6/2)^2)}}}}={{{(40+(6/2)^2)}}}
 
{{{(x^2-6x+(3)^2)}}}={{{(40+(3)^2)}}}
{{{(x^2-6x+(3)^2)}}}= {{{(40+(9))}}}

{{{(x^2-6x+(3)^2)}}}=49
{{{(x-3)(x-3))}}}=49 [factor]
{{{(x-3)^2)}}}= 49

{{{(sqrt((x-3)^2)))}}}= {{{(sqrt( 49))}}}
x-3=+-7
x=3+-7
x=3+7=10
or
x=3-7=-4
.
Solution: (10 or -4)