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**Malubia****Member**- Registered: 2018-12-06
- Posts: 3

Sir how you derived this formula "x = ta + (1−t)b" in

https://www.mathsisfun.com/calculus/concave-up-down-convex.html

Please explain me this formula.I didn't get it

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,462

hi Malubia

Welcome to the forum.

That had me puzzled for a while.

Draw a horizontal line AB across from point A = ( a, f(a) ) to B = ( b, f(a) ) with a point X = (x , f(a) ) anywhere between A and B.

Define t to be the fraction XB/AB.

Then

Hope that helps,

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob Bundy

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**Malubia****Member**- Registered: 2018-12-06
- Posts: 3

@bob bundy

Thank you bob. May you live for thousand years

*Last edited by Malubia (2018-12-06 21:42:40)*

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