Equation of a Straight Line

(i) Write down the co-ordinates of the point P that divides the line joining A ( ā€“ 4, 1) and B (17, 10) in the ratio 1 : 2.
(ii) Calculate the distance OP where 0 is the origin
(iii) In what ratio does the y-axis divide the line AB?

(i) Given, co-ordinates of the line joining A ( ā€“ 4, 1) and B (17, 10) and point P divides the line segment in the ratio 1 : 2 Let the co- ordinates of P be (x, y) Then,  

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ABCD is a rhombus. The co-ordinates of A and C are (3, 6) and ( ā€“ 1, 2) respectively. Write down the equation of BD.ABCD is a rhombus. The co-ordinates of A and C are (3, 6) and ( ā€“ 1, 2) respectively. Write down the equation of BD.

Solution: Given, ABCD is a rhombus and co-ordinates of A are (3, 6) and of C are (-1, 2) Slope of AC (m1) = (2 ā€“ 6)/ (-1 ā€“ 3) = -4/-4 = 1 We know that, the diagonals of a rhombus bisect each other...

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The vertices of a triangle are A (10, 4), B (4, ā€“ 9) and C (ā€“ 2, ā€“ 1). Find the equation of the altitude through A. The perpendicular drawn from a vertex of a triangle to the opposite side is called altitude.

Solution: Given, vertices of a triangle are A (10, 4), B (4, ā€“ 9) and C (ā€“ 2, ā€“ 1) Now, Slope of line BC (m1) = (-1 + 9)/ (-2 ā€“ 4) = 8/ (-6) = -4/3 Let the slope of the altitude from A (10, 4) to BC...

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The equation of a line is 3x + 4y ā€“ 7 = 0. Find (i) the slope of the line. (ii) the equation of a line perpendicular to the given line and passing through the intersection of the lines x ā€“ y + 2 = 0 and 3x + y ā€“ 10 = 0.

Solution: Given line equation: 3x + 4y ā€“ 7 = 0 (i) Slope of the line is given by, 4y = -3x + 7 y = (-3/4) x + 7 Hence, slope (m1) = -3/4 (ii) Let the slope of the perpendicular to the given line be...

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The equation of a line is y = 3x ā€“ 5. Write down the slope of this line and the intercept made by it on the y-axis. Hence or otherwise, write down the equation of a line which is parallel to the line and which passes through the point (0, 5).

Solution: Given line: y = 3x ā€“ 5 Here slope (m1) = 3 Substituting x = 0, we get y = ā€“ 5 Hence, the y-intercept = ā€“ 5 Now, the slope of the line parallel to the given line will be 3 and it passes...

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Point A (3, ā€“ 2) on reflection in the x-axis is mapped as Aā€™ and point B on reflection in the y-axis is mapped onto Bā€™ ( ā€“ 4, 3). (i) Write down the co-ordinates of Aā€™ and B. (ii) Find the slope of the line Aā€™B, hence find its inclination.

Solution: Given, Aā€™ is the image of A (3, -2) on reflection in the x-axis. (i) The co-ordinates of Aā€™ will be (3, 2). Again Bā€™ (- 4, 3) in the image of Aā€™, when reflected in the y-axis Hence, the...

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Three vertices of a parallelogram ABCD taken in order are A (3, 6), B (5, 10) and C (3, 2) find: (i) the coordinates of the fourth vertex D. (ii) length of diagonal BD.Three vertices of a parallelogram ABCD taken in order are A (3, 6), B (5, 10) and C (3, 2) find: (i) the coordinates of the fourth vertex D. (ii) length of diagonal BD.

Solution: Given, the three vertices of a parallelogram ABCD taken in order are A (3, 6), B (5, 10) and C (3, 2) (i) We know that the diagonals of a parallelogram bisect each other. Let (x, y) be the...

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The given figure represents the line y = x + 1 and y = āˆš3x ā€“ 1. Write down the angles which the lines make with the positive direction of the x-axis. Hence determine Īø.

Solution: Given line equations, y = x + 1 and y = āˆš3x ā€“ 1 On comparing with y = mx + c, The slope of the line: y = x + 1 is 1 as m = 1 So, tan Īø = 1 ā‡’ Īø = 45o And, The slope of the line: y = āˆš3x ā€“ 1...

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