Question

The lines AB and CB intersect at B

(a) Find the co-ordinates of the midpoint of AB
(b) Find the equation of the line CB​

Answer 1

Explanation:

Soln

given,

from the figure

coordinate of B is (5,3),

A(7,0) and C(0,4)

A. solution

let, M(x,y) be the mid point of AB

A(7,0) = (x1,y1)

B(5,3) = (x2,y2)

we know

x = (x2+x1)/2

or, x = (5+7)/2

or, x = 12/2

or, x = 6

and for y

y = (y2+y1)/2

or, y = (3+0)/2

or, y = 3/2

therefore M(x,y) = (6,3/2)

B. solution

let,

C(0,4) = (x1,y1)

B(5,3) = (x2,y2)

equation of line is ;

(y - y1)/(x - x1) = (y2 - y1)/(x2 - x1)

or, (y - 4)/(x -0) = (3 - 4)/(5 - 0)

or, (y - 4)/(x - 0) = -1 / 5

by cross multiply

or, 5×(y - 4) = -1×(x)

or, 5y - 20 = -x

or, x + 5y = 20 is the required equation.