Answer:
A = -2
B = -8
Explanation:
A system of equations has infinitely many solutions when both equations are exactly the same equation, then both graphs intersect in infinitely many points, meaning that the system has infinitely many solutions.
Then if we have the equations:
A*x- y = 8
2*x + y = B
We want to find A and B such that both equations are exactly the same thing.
Notice that in the first one we have negative y, while in the second we have positive y.
Then A needs to be minus the coefficient that multiplies x in the other equation, this means that:
A = -2
And B needs to be minus the corresponding therm in the other equation, then B = -8.
Then the system becomes:
-2*x - y = 8
2*x + y = -8
We can see that one equation is -1 times the other, so if we write both of them as linear equations in the slope-intercept form, we get:
y = -8 - 2*x
y = -8 - 2*x
So both equations are exactly the same thing, meaning that we have infinitely many solutions.