Answer with explanation:
Let us assume that the 2 functions are:
1) f(x)
2) g(x)
Now by definition of concave function we have the first derivative of the function should be strictly decreasing thus for the above 2 function we conclude that

Now the sum of the 2 functions is shown below

Diffrentiating both sides with respect to 'x' we get

Since each term in the right of the above equation is negative thus we conclude that their sum is also negative thus

Thus the sum of the 2 functions is also a concave function.
Part 2)
The product of the 2 functions is shown below

Diffrentiating both sides with respect to 'x' we get

Now we can see the sign of the terms on the right hand side depend on the signs of the function's themselves hence we remain inconclusive about the sign of the product as a whole. Thus the product can be concave or convex.
Which is it
2x times y times 3 = 6xy
or,
2xxyx3= 6x^3y
First, write the rate as a decimal by moving the decimal point two places to the left from the percent.
r = 5% = 0.05
C = p + rp
C = 30.99 + 0.05 * 30.99
C = 30.99 + 1.55
C = 32.54
Answer: The total cost is $32.54
2y-6=34 is the needed equation
B is true; pi= ~3.14. 3+4 is equal to 7, so because pi is greater than 3, pi+4>7