# Given that #cosh3x+3coshx=4cosh^3x# how do you show that #k^3 = 3k - 4# has a root in between #-3# and #-2# and choose a suitable value of #y# for #k=ycoshx# and calculate the root?

##### 1 Answer

Dec 14, 2016

The real root is

#### Explanation:

Making

dividing both sides by

making now

comparing now with the identity

we conclude

Solving for

and finally

As we can observe