Question

X + y = k

x - y = k
The solution to the system shown is _____.
(0, k)
(2, 2)
(k, 0) User: 3x - 4y = 7
3x + 2y = -5
When the second equation is subtracted from the first, the resulting equation is _____.
-6y = -12
-6y = 12
-2y = -12
2y = 12

Answer 1

If x+y=k, then x=k-y. Substitute k-y for x in the other equation. So (k-y)-y=k. k-2y =k which means y has to be 0 (both k's subtract on both sides). -2y=0. The answer: (k,0). For the second part, get all the parts of the equations on both sides; (make both sides equal zero) 3x-4y-7 and 3x+2y+5. Then subtract. 3x-4y-7-(3x+2y+5) Make it equal to zero again and solve! :) -6y-12=0 -6y=12!! ta da!