(C) f(a,b+k)
(D) f(a,b)
5.
Given
that
ft (1, 2) = f, (1,2)=0,
fr (1,2)= 6
and
fa (1,2) fwy (1,2) - f> (1, 2) = 72. Then the function f has
at (1,2)
(A) minimum
(B) maximum
(C) Both maximum and minimum
(D) None of these
131
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Answered by
1
Answer:
Step-by-step explanation:
With this setup (a/b=c/d=e/f) you can only ever express one variable in terms of 3 others, but I just wanted to put in a good word for one of my favourite little rules that sadly does not get much publicity today: The Rule of Threes.
Basically, if you have three numbers a, b, c, such that, a/b = c/d (also represented as ratios or proportions, a:b = c:d, or “a is to b what c is to d”) then you can calculate any one of them using the other 3 known values by multiplying on the diagonal that doesn’t contain the unknown, then dividing by the remaining number.
Here’s how it works:
ab=cd
Then you have the following:
a=b×cd , b=a×dc , c=a×db , etc.
(Easily proved by solving the standard way: bringing fractions to same denominator, then isolating your unknown, etc. — but it saves at least 2 steps in your calculations.)
Comes in handy for ratio and direct proportions problems (“if 20 soldiers eat 15 kg potatoes, how many will 45 soldiers eat?” :-) ), trigonometry, physics formulae, etc. Please teach the kiddies (of course, these days you have online calculators even for this…)
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