Question

The centre of a circle is 2a-7,7 and it passes through the point -3,-1 if the diameter of the circle is 20 units find a

Answer 1

Answer:

a = 5

Step-by-step explanation:

Diameter = 20

=> radius = 10

=> distance from centre (2a-7, 7) to point (-3,-1) = 10

=> ( (2a-7) - (-3) )²  +  ( 7 - (-1) )²  =  10²

=> ( 2a -7 + 3 )²  +  ( 7 + 1 )²  =  100

=> ( 2a - 4 )²  +  8²  = 100

=> 4a² - 16a + 16 + 64 = 100

=> a² - 4a + 4 + 16 = 25

=> a² - 4a - 5 = 0

=> ( a - 5 ) ( a + 1 ) = 0

=> a = 5 or a = -1

=> a = 5   ( since a cannot be negative ).