NRICH: Negatively Triangular

How many intersections do you expect from four straight lines ? Which three lines enclose a triangle with negative co-ordinates for every point ?

Four straight lines have the following equations:

3y+2x= 19

How many points of intersections do you expect there to be?

Three of the four lines enclose a triangle which only has negative co-ordinates for all points on that triangle.

Which three lines?

Age 14 to 16

Algebra & Pre-Algebra, Functions & Graphs, Linear Equations
High School, Educator

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NRICH (University of Cambridge)

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