## Question

secondary 4 | E Maths

Anyone can contribute an answer, even non-tutors.

##### Chloe

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Plz solve with steps thanks

Date Posted: 1 year ago
Views: 359

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1st
hope this helps.
Date Posted: 1 year ago
Chloe
1 year ago
How did px suddenly became this (12-2.4x)
Snell
1 year ago
it is not P(x),
it is P'(x), a derivative of P(x).
meaning
differentiate P(x) wrt x
Chloe
1 year ago
Ok thanks for your help! Though we do not learn differentiation in sec 4
Snell
1 year ago
oh, u dun take AMath?

then to find the max. u hv to follow a tedious method of completing the square to find the max point.

complete the square:
P(x) = -1.2x² + 12x - 5
= -1.2(x²-10x) - 5
= -1.2(x²-10x+25) - 5 +30
= -1.2(x-5)² + 25

this means max pt is at (5, 25).

how?
bcos of (x-5)², we know the x-coordinates of max pt is 5.
[equate x-5=0 => x=5]

then subst. x=5 into P(x):
P(x) = -1.2(5-5)² + 25
= 0 + 25 = 25

max profit P(x) = 25.

and

u r welcome!
Chloe
1 year ago
This is what im looking for thank you so much
Chloe
1 year ago
So the ans would be 25000?
Snell
1 year ago
nope. sorry.

the qn asks for quantity of products, i.e. x ;
we found x = 5 ;

so the ans is 5000, bcos the qn states x is in thousands.