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C2 differentiation help

I got the equation down to 3(x-1)(x-1) > 0, the answer in the back of the book is 'x e r =(with a line through it) 1. Does that just mean the answer is anything apart from 1?

Reply 1

Indeterminate

Original post by physicshelpme

I got the equation down to 3(x-1)(x-1) > 0, the answer in the back of the book is 'x e r =(with a line through it) 1. Does that just mean the answer is anything apart from 1?

Yes, because

f(x)=3(x-1)^2

is positive everywhere apart from at the point where x=1 (it touches the x axis here, and is therefore 0).

Reply 2

physicshelpme

Thought so, okay the next one has confused me as well.

'Find the values of x for which f(x) is an increasing function, given that f(x) equals:

5x^3 + 12x
I differentiated to get 15x^2 + 12 > 0
3(5x^2 + 4) > 0 and now I don't know what to do