Part (a)
You have plotted the point (2,-1) in the correct location. Starting from this anchor point, move down 4 and right 5 to arrive at (7,-5).
This "down 4, right 5" movement pattern is from the slope -4/5
See diagram below.
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Part (b)
y = mx+b
-1 = (-4/5)(2) + b
-1 = -8/5 + b
b = -1 + 8/5
b = -5/5 + 8/5
b = (-5+8)/5
b = 3/5
This is where the line crosses the vertical y axis.
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Part (c)
m = -4/5 is the given slope
b = 3/5 was the y intercept found in the previous section
y = mx+b
y = (-4/5)x + 3/5
5y = 5( (-4/5)x + 3/5 )
5y = -4x + 3
