#color(brown)("This part in great detail to demonstrate first principles")#
Multiply everything inside the bracket by the #x# that is outside giving:
#" "3x-x^2" "=" "-3#
To make the #x^2# positive add #x^2# to both sides
#" "color(green)(3x-x^2color(red)(+x^2)" "=" "-3color(red)(+x^2)) #
But #-x^2+x^2=0#
#" "3x+0" "=" "x^2-3#
Subtract #color(red)(3x)# from both sides
#color(green)(" "3xcolor(red)(-3x)" "=" "x^2-3color(red)(-3x)#
#" "0" "=" "x^2-3x-3#
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#color(brown)("Calculated much faster now")#
Standard form #->y=ax^2+bx+c#
where #x=(-b+-sqrt(b^2-4ac))/(2a)#
#x=(-(-3)+-sqrt((-3)^2-4(1)(-3)))/(2(1))#
#x=3/2+-sqrt(9+12)/2#
#x=3/2+-sqrt(21)/2 larr" exact values"#
#x~~3.791" ; "x~~-0.791#
