1. Determine if the points `A(1,5), B(2,3), C(-2,-11)` are collinear pointsSolution:We know that the distance between the two points `(x_1,y_1)` and `(x_2,y_2)` is
`d=sqrt((x_2-x_1)^2+(y_2-y_1)^2)`
The given points are `A(1,5),B(2,3),C(-2,-11)`
`AB=sqrt((2-1)^2+(3-5)^2)`
`=sqrt((1)^2+(-2)^2)`
`=sqrt(1+4)`
`=sqrt(5)`
`:. AB=sqrt(5)`
`BC=sqrt((-2-2)^2+(-11-3)^2)`
`=sqrt((-4)^2+(-14)^2)`
`=sqrt(16+196)`
`=sqrt(212)`
`:. BC=2sqrt(53)`
`AC=sqrt((-2-1)^2+(-11-5)^2)`
`=sqrt((-3)^2+(-16)^2)`
`=sqrt(9+256)`
`=sqrt(265)`
`:. AC=sqrt(265)`
As, AC > AB and AC > BC
If points A, B and C are collinear then AB + BC = AC
But `sqrt(5)+2sqrt(53)=16.7963!=sqrt(265)`
`:.` A,B,C are not collinear points
2. Determine if the points `A(1,-3), B(2,-5), C(-4,7)` are collinear pointsSolution:We know that the distance between the two points `(x_1,y_1)` and `(x_2,y_2)` is
`d=sqrt((x_2-x_1)^2+(y_2-y_1)^2)`
The given points are `A(1,-3),B(2,-5),C(-4,7)`
`AB=sqrt((2-1)^2+(-5+3)^2)`
`=sqrt((1)^2+(-2)^2)`
`=sqrt(1+4)`
`=sqrt(5)`
`:. AB=sqrt(5)`
`BC=sqrt((-4-2)^2+(7+5)^2)`
`=sqrt((-6)^2+(12)^2)`
`=sqrt(36+144)`
`=sqrt(180)`
`:. BC=6sqrt(5)`
`AC=sqrt((-4-1)^2+(7+3)^2)`
`=sqrt((-5)^2+(10)^2)`
`=sqrt(25+100)`
`=sqrt(125)`
`:. AC=5sqrt(5)`
As, BC > AB and BC > AC
If points A, B and C are collinear then AB + AC = BC
Here `sqrt(5)+5sqrt(5)=6sqrt(5)`
`:.` A,B,C are collinear points
3. Determine if the points `A(-1,-1), B(1,5), C(2,8)` are collinear pointsSolution:We know that the distance between the two points `(x_1,y_1)` and `(x_2,y_2)` is
`d=sqrt((x_2-x_1)^2+(y_2-y_1)^2)`
The given points are `A(-1,-1),B(1,5),C(2,8)`
`AB=sqrt((1+1)^2+(5+1)^2)`
`=sqrt((2)^2+(6)^2)`
`=sqrt(4+36)`
`=sqrt(40)`
`:. AB=2sqrt(10)`
`BC=sqrt((2-1)^2+(8-5)^2)`
`=sqrt((1)^2+(3)^2)`
`=sqrt(1+9)`
`=sqrt(10)`
`:. BC=sqrt(10)`
`AC=sqrt((2+1)^2+(8+1)^2)`
`=sqrt((3)^2+(9)^2)`
`=sqrt(9+81)`
`=sqrt(90)`
`:. AC=3sqrt(10)`
As, AC > AB and AC > BC
If points A, B and C are collinear then AB + BC = AC
Here `2sqrt(10)+sqrt(10)=3sqrt(10)`
`:.` A,B,C are collinear points
4. Determine if the points `A(0,-1), B(3,5), C(5,9)` are collinear pointsSolution:We know that the distance between the two points `(x_1,y_1)` and `(x_2,y_2)` is
`d=sqrt((x_2-x_1)^2+(y_2-y_1)^2)`
The given points are `A(0,-1),B(3,5),C(5,9)`
`AB=sqrt((3-0)^2+(5+1)^2)`
`=sqrt((3)^2+(6)^2)`
`=sqrt(9+36)`
`=sqrt(45)`
`:. AB=3sqrt(5)`
`BC=sqrt((5-3)^2+(9-5)^2)`
`=sqrt((2)^2+(4)^2)`
`=sqrt(4+16)`
`=sqrt(20)`
`:. BC=2sqrt(5)`
`AC=sqrt((5-0)^2+(9+1)^2)`
`=sqrt((5)^2+(10)^2)`
`=sqrt(25+100)`
`=sqrt(125)`
`:. AC=5sqrt(5)`
As, AC > AB and AC > BC
If points A, B and C are collinear then AB + BC = AC
Here `3sqrt(5)+2sqrt(5)=5sqrt(5)`
`:.` A,B,C are collinear points
5. Determine if the points `A(2,8), B(1,5), C(0,2)` are collinear pointsSolution:We know that the distance between the two points `(x_1,y_1)` and `(x_2,y_2)` is
`d=sqrt((x_2-x_1)^2+(y_2-y_1)^2)`
The given points are `A(2,8),B(1,5),C(0,2)`
`AB=sqrt((1-2)^2+(5-8)^2)`
`=sqrt((-1)^2+(-3)^2)`
`=sqrt(1+9)`
`=sqrt(10)`
`:. AB=sqrt(10)`
`BC=sqrt((0-1)^2+(2-5)^2)`
`=sqrt((-1)^2+(-3)^2)`
`=sqrt(1+9)`
`=sqrt(10)`
`:. BC=sqrt(10)`
`AC=sqrt((0-2)^2+(2-8)^2)`
`=sqrt((-2)^2+(-6)^2)`
`=sqrt(4+36)`
`=sqrt(40)`
`:. AC=2sqrt(10)`
As, AC > AB and AC > BC
If points A, B and C are collinear then AB + BC = AC
Here `sqrt(10)+sqrt(10)=2sqrt(10)`
`:.` A,B,C are collinear points
This material is intended as a summary. Use your textbook for detail explanation.
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