Using the two coordinates you can find the equation
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Find slope first
Slope [tex]= \frac{y2-y1}{x2-x1} [/tex]
0 - 3 = -3
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-4 - 0 = -4
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Simplify -3/-4
3/4
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Your slope is 3/4 and the Y-intercept as mentioned in the question is "3"
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So your equation is y = 3/4x + 3