How do you solve the system by addition #–2x – 3y = –17# and #x + 4y = 16#?
first, you must have opposite terms in x or in y, in this case to join this for x you simply must multiply all terms of the second equation by 2 to have:
now you can sum the terms of the equations to have:
and, by symplifying, you have:
You can go on by substitution to have x, but if you again use addition, you can multiply the terms of the first equation by 4 and the terms of the second equation by 3, to have opposite terms in both equations (-12y and +12y):
Then, by adding all terms of the first one to all terms of the second one:
and, by symplifying: