Question 665332
Hi. 
I always say to think of the equals sign as a balance point, and whatever
you do to one side you must do to the other side, or else you will
throw the equation out of balance.
{{{ x + 2 + x - 5 + 2x - 1 + x^2 - 3x = 70 }}}
Group the {{{ x }}} terms and constant terms together
{{{ x^2 + x + x + 2x - 3x + 2 - 5 - 1 = 70 }}}
Add the {{{ x }}} terms and constant terms
{{{ x^2 + x - 4 = 70 }}}
Subtract {{{ 70 }}} from both sides
{{{ x^2 + x - 74 }}}
Use the quadratic equation
{{{ x = (-b +- sqrt( b^2 - 4*a*c )) / (2*a) }}}
{{{ a = 1 }}}
{{{ b = 1 }}}
{{{ c = -74 }}}
{{{ x = ( -1 +- sqrt( 1^2 - 4*1*(-74) )) / (2*1) }}}
{{{ x = ( -1 +- sqrt( 1 + 296 )) / 2 }}}
{{{ x = ( -1 +- sqrt( 297 )) / 2 }}}
{{{ x = ( -1 + 17.234 ) / 2 }}}
{{{ x = 16.234 / 2 }}}
{{{ x = 8.117 }}}
that would make the sides:
{{{ x + 2 = 10.117 }}}
{{{ x - 5 = 3.117 }}}
{{{ 2x - 1 = 15.234 }}}
{{{ x^2 - 3x = 65.886 - 24.351 }}}
{{{ x^2 - 3x = 41.535 }}}
---------------------
Adding these:
{{{ 10.117 + 3.117 + 15.234 + 41.535 = 70.003 }}}
close enough