Posted by lisa on Thursday, December 4, 2008 at 8:43pm.
y = mx + b, and you're right, we do not know the y-intercept here.
so, y = (2/5)x + b.
They tell us the X-intercept is 4.5. How does this help us? The x-intercept is where it crosses the x-axis. At that point, y = 0. So, the line crosses the point (4.5,0).
So, now we substitute in 0 for y and 4.5 for x:
0 = (2/5)(4.5) + b.
We can solve for b, and we get
b= -9/5.
So, we now have our y-intercept, and use y = mx + b.
Does this make sense??
thank you =D
you're welcome!
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