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    Question

    What is the area of triangle ABC with vertices A(1, 2),

    B(5, 6), and C(7, 2)?
    A 12 Correct Answer Incorrect Answer
    B 18 Correct Answer Incorrect Answer
    C 10 Correct Answer Incorrect Answer
    D 24 Correct Answer Incorrect Answer

    Solution

    ATQ, Use the coordinate area formula: Area = (1/2) Β· |x₁(yβ‚‚ βˆ’ y₃) + xβ‚‚(y₃ βˆ’ y₁) + x₃(y₁ βˆ’ yβ‚‚)|. Let A(1,2) β†’ (x₁,y₁), B(5,6) β†’ (xβ‚‚,yβ‚‚), C(7,2) β†’ (x₃,y₃). Compute: yβ‚‚ βˆ’ y₃ = 6 βˆ’ 2 = 4 y₃ βˆ’ y₁ = 2 βˆ’ 2 = 0 y₁ βˆ’ yβ‚‚ = 2 βˆ’ 6 = βˆ’4 x₁(yβ‚‚ βˆ’ y₃) = 1 Γ— 4 = 4 xβ‚‚(y₃ βˆ’ y₁) = 5 Γ— 0 = 0 x₃(y₁ βˆ’ yβ‚‚) = 7 Γ— (βˆ’4) = βˆ’28 Sum = 4 + 0 βˆ’ 28 = βˆ’24 Area = (1/2) Β· |βˆ’24| = 12 square units.

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