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Answer: y < -4x+3</h3>
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We need to find the equation for the boundary line. It goes through the two points (1,-1) and (2,-5)
Find the slope of the line through (x1,y1) = (1,-1) and (x2,y2) = (2,-5)
m = (y2 - y1)/(x2 - x1)
m = (-5 - (-1))/(2 - 1)
m = (-5 + 1)/(2 - 1)
m = -4/1
m = -4 is the slope
Plug m = -4 and (x1,y1) = (1,-1) into the point slope formula. Solve for y.
y - y1 = m(x - x1)
y - (-1) = -4(x - 1)
y + 1 = -4(x - 1)
y + 1 = -4x + 4 ... distributing
y + 1 - 1 = -4x + 4 - 1 ... subtracting 1 from both sides
y = -4x + 3 is the equation of the boundary line
The blue shaded region tells us to consider all points below this boundary line as solutions. So we will use a "less than" sign to indicate this
We go from y = -4x+3 to y < -4x+3 which is the answer we want.
We do not have a line under the inequality sign. Simply because the boundary is a dashed line, so we exclude points on the boundary line as solutions. If we had , then the boundary line would be solid and it would tell the reader "points on the boundary line are part of the solution set".