Question 4821
hi, this is a classic problem area for students - basically because mathematicians are lazy and we miss out some notation, because we assume everybody knows this, but of course when you are learning maths, you do not know everything :-). So,


{{{2x + 5x -3(4 + 3) = -21}}} is really {{{2*x + 5*x -3*(+4 + 3) = -21}}} --> the 4 has a + sign in front of it too, because it is the number +4, but the software is being "clever" and not showing it, because it assumes everybody knows it is there!


So, for the bracket, we have the number -3 to be multiplied with both +4 and +3 within the bracket:


(-3)*(+4) is -12
(-3)*(+3) is -9


so, the equation becomes 2x + 5x -12 -9 = -21


We can now collect like terms together on the lefthand side: 7x - 19 = -21 which becomes 7x = -2 etc


As for {{{2x + 5x + 3(4 - 3) = -21}}}, again we have:


(+3)*(+4) is +12
(+3)*(-3) is -9


--> {{{2x + 5x + 12 - 9 = -21}}}


Hope this is clearer for you?


jon.