Question
Mon October 15, 2012 By: Manisha Mohanty

IN THE SOLUTION OF THE QUESTION GIVEN BELOW TO FIND THE REAL ROOTS OF THE GIVEN EQUATION ,SIR WHY CANNOT WE WRITE k > and = to -4?

Expert Reply
Tue October 16, 2012

For k greater than or equal to -4, consider k = 0.

In such case, k2 - 16 = 02 - 16 = 0 - 16 = -16 which is not greater than or equal to zero.

 

Use the following shortcut to solve such problems;

        i.            If x2 is greater than or equal to a2, for a being a positive number, then (x is greater than or equal to a) or (x is less than or equal to -a).

      ii.            If x2 is less than or equal to a2, for a being a positive number, then (x is less than or equal to a) or (x is greater than or equal to -a).

 

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