aruthmetic progressions

Asked by  | 28th Jan, 2009, 07:47: AM

Expert Answer:

a,b,c are in A.P.





So, the equation of the line ax+by+c=0

can be written as


So we get,



Now if (1,-2) has to lie on this line, we must have that the coordinates of this point  always satisfy the equation .

So, putting  x=1, y= -2 in the equation of the line we get,




So we see that the point (1,-2) satisfies the equation of the line whatever may be the values of  a,b,c as long as they are in A.P.

Hence proved.

Answered by  | 28th Jan, 2009, 10:10: AM

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