Year 12s: what will be the first way you research your future options? >>

Year 12s: what will be the first way you research your future options? >>

Year 12s: what will be the first way you research your future options? >>

Triangle Inequality questions

right the question is prove that |b|<1/2 implies |(b^3) -1|> 7/8

and the solution goes |b^3 - 1| >= ||b^3| - 1|>= 1-|b^3|... and i don't get they got to the last part

Its probably sdomething very simple if someone could explain that'd be great :smile:

:smile:

Thanks

Original post by _-_MandsSs_-_

right the question is prove that |b|<1/2 implies |(b^3) -1|> 7/8

and the solution goes |b^3 - 1| >= ||b^3| - 1|>= 1-|b^3|... and i don't get they got to the last part

Its probably sdomething very simple if someone could explain that'd be great :smile:

:smile:

Thanks

Well given the restriction on b, is

|b^3|-1

positive or negative? Hence when you remove the outer modulus signs .... That final ">=" could be replaced with just "=".

Start with what you're given being equivalent to -1/2 < b < 1/2

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