Answer:
6 knots
Step-by-step explanation:
Let the speed be v knots
then time taken to cover 500 M = 500 / v hrs
fuel consumption /hr = 216 + 0.5v^3
let F be the fuel consumption for trip
= [500/v][216 + 0.5v^3]
= 500[216/v + 0.5v^2]
dF/dv = 500[ - 216/v^2 + v]
d^2F/d^2v = 500[432/v^3 + 1] , i.e. +ve
so setting dF/dv will give a minima
500[ -216/v^2 + v] = 0
or v = 216/v^2
or v^3 = 216
solving, we get v = [216]^(1/3) = 6 knots
the smaller number is 13 and the larger one is 18.
Let's say that the smaller number is x and the larger one is y.
Giving the equation x + 5 = y
This would also make the equation y^2-x^2= 155
to solve let's simplify to find what y^2 is in x terms.
y^2 = (x+5) (x+5) = x^2 +10x + 25.
therefore x^2 + 10x + 25 -x^2= 155
10x + 25 = 155
10x = 130
x = 13
y = 18
To find the cofactor of
![A=\left[\begin{array}{ccc}7&5&3\\-7&4&-1\\-8&2&1\end{array}\right]](https://tex.z-dn.net/?f=A%3D%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D7%265%263%5C%5C-7%264%26-1%5C%5C-8%262%261%5Cend%7Barray%7D%5Cright%5D)
We cross out the Row and columns of the respective entries and find the determinant of the remaining 
matrix with the alternating signs.
Therefore in increasing order, we have;
12 x 2+40=64
Malia is 12 years old.
