Thread: Minimise A= 1/2(1-x+qx^2)

Hey, got a question, my sis has exams tomorrow and she cant solve this,...its been 7 years ive done this lvl of maths, and dont remember enough to help her...any help ?

Its part of the question

Show A= 1/2(1-x+qx^2)

Given that x can vay, show that Qy=Yr when A is a min and express the min of A in terms of q

First part she did, now 2nd part

I forgot, PQRS is a square

A is the area of triangle sxy, and q is a constant...

Still dont get it

Btw, its an o level question for may 02

sorry, some info was missing in the first diagram

is quadratic. You can rewrite it as and complete the square: . Since a square is never negative, this will be a minimum (assuming q is positive) when x= 1/(2q) and that minimum will be .

Thanks, have been able to solve it