? asked in 科學及數學數學 · 1 decade ago

Rectangle Coordinates System

P(4,1) and Q(-3,2) are two given points and R(x,y) is a variable point.

a) Find the area of the trangle PQR in terms of x and y.

b) If R lies on the y-axis and the area of trangle PQR is 12 square units,

find the coordinates of R

1 Answer

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  • wy
    Lv 7
    1 decade ago
    Favorite Answer

    a) Please refer to additional mathematics textbook on co-ordinate geometry and area of triangle.

    b) Since R is on the y-axis, its co-ordinates will be (0,y).

    1) Area of trapezium QR with the x-axis = 3(2+y)/2.

    2) Area of trapezium RP with the x-axis = 4(1+y)/2.

    3) Area of trapezium QP with the x-axis = 7(1 + 2)/2.

    (1) + (2) - (3) = 12, therefore y=5. So R is (0,5).

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