Answer:
Simultaneous equations are two or more algebraic equations that share variables e.g. x and y . They are called simultaneous equations because the equations are solved at the same time. Each of these equations on their own could have infinite possible solutions.
Simple....
x<6
This means that on your graph at 6 it's a circle (not colored in) and it goes to the left indefinitely...
Thus, your answer.
D is a notation for differential. There is a d2 in your formula because in the numerator there are two differentials. The formula is thus the second derivative of a function with respect to two variables.
The plane speed in still air is the average of the two speeds: 430 miles/hour.
The wind speed is half the difference of the two speeds: 20 miles/hour.
