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For what value of X are the points A (-3, 12), B (7, 6) and C (x, 9) collinear.

Solution

✅ Correct Option: 3

For collinearity, slope AB = slope BC. Slope AB =6−127−(−3)=−610=−35= \frac{6-12}{7-(-3)} = \frac{-6}{10} = -\frac{3}{5}.

Slope BC =9−6x−7=3x−7= \frac{9-6}{x-7} = \frac{3}{x-7}. Setting equal: −35=3x−7⇒−3(x−7)=15⇒x=2-\frac{3}{5} = \frac{3}{x-7} \Rightarrow -3(x-7) = 15 \Rightarrow x = 2.

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