Solve each system graphicaly. be sure to check your solution. if a system has an infinite number of solutions, use set-builder notation to write a solution set. If a system has no solution, state this.
4x - y = 9,
x - 3y =16

Question

saifoo.khan · Answer

i got the solutions! :O

anonymous · Answer

answer or method?

anonymous · Answer

method

saifoo.khan · Answer

lol, i got both!

anonymous · Answer

multiply the first equation all the way across by -3

anonymous · Answer

$$-12x+3y=-27$$

anonymous · Answer

then add in a line to the two equations  together.  you get 
$$-12x+3y=-27$$
$$x-3y=16$$
$$-11x=-11$$
$$x=1$$

anonymous · Answer

now that you know x = 1 replace x by 1 in either equation to find y

anonymous · Answer

the first one gives 
$$4\times 1-y=9$$
$$4-y=9$$
$$-y=5$$
$$y=-5$$

anonymous · Answer

so solution is 
$$x=1,y=-5$$ or 
$$(1,-5)$$