Relative Position of a Point with Respect to a Line
Number of int...
Question
Number of integral coordinates strictly lying inside the triangle formed by the line x+y=21 with coordinate axes are
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Solution
Triangle formed will have vertices as O(0,0),A(21,0)andB(0,21) If x=1, Point on the hypotenuse ≡(1,20) So, number of integral points lying inside triangle when x=1 is 19 i.e {(1,1),(1,2)⋯(1,19)} Similarly, when x=2, number of integral points lying inside triangle is 18 i.e {(2,1),(2,1)⋯(2,18)} ∴ Total number of integral points lying inside triangle are ⇒19+18+17+⋯+1 =19×202=190