y = 1/2 log(x + 1) - log(2x + 10)
The y-intercept of any graph is the point where x=0.
y = 1/2 log(0 + 1) - log(0 +10)
y = 1/2 log(1) - log(10)
log(1) = 0
log(10) = 1
y = 1/2 (0) - 1
y = -1
That's all there is to it. I'll bet you totally froze when you saw all those logs.