Question 1082737: I'm trying to solve the system using substitution. I don't understand it. The problem is ~ -7x-2y=-13
x-2y=11 Answer by ikleyn(52781) (Show Source):
-7x -2y = -13, (1)
x - 2y = 11 (2)
Look into equation (2). Express x = 11 + 2y from it.
Do you understand how I did it? - I simply added 2y to both sides of the equation (2).
So, I obtained this: x = 11 + 2y.
Now I substutute it into equation (1), replacing x there:
-7*(11+2y) - 2y = -13.
It is a single equation for "y".
It is much easier to solve it. Simplify:
-77 - 14y - 2y = -13,
-16y = -13 + 77,
-16y = 64 ----> y = = -4.
OK. We just found y= -4.
Now substitute it into equation (2). You will get
x - 2*(-4) = 11 ----> x + 8 = 11 ----> x = 11-8 ----> x= 3.
Answer. The solution is x= 3, y= -4.
Solved.
Do you understand this explanation ?
If you do, then you know now how the substitution method works.
