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The perpendicular distance from the point $(-2,-3)$ to the line $12x+16y+12=0$ is:
A2 units
B3 units
C5 units
D6 units
Answer & Solution
Correct answer: B. 3 units
1. Use $d=\left|\dfrac{Ah+Bk+C}{\sqrt{A^2+B^2}}\right|$ with $A=12$, $B=16$, $C=12$.
2. Numerator: $12(-2)+16(-3)+12=-24-48+12=-60$.
3. Denominator: $\sqrt{12^2+16^2}=\sqrt{144+256}=\sqrt{400}=20$.
4. $d=\left|\dfrac{-60}{20}\right|=3$ units.
5. Forgetting the modulus or dropping the constant term $12$ produces the other values.
_Source: NECTA ACSEE 2023 Advanced Mathematics 142/1, Question 8: Coordinate Geometry I_