y-4=4x+3y=-(9-x)

What is the value of xy?

3 answers

what are we to make of the two = signs?
I believe it's like:
y-4=4x+3y
y-4=-(9-x)
4x+3y=-(9-x)
well, then we have

y-4 = 4x+3y
2y = -4x-4
y = -2x-2

y-4 = -(9-x)
y-4 = x-9
y = x-5

So,

-2x-2 = x-5
x = 1
and thus y = -4

xy = -4