Evaluate the function. f(x)=-x^2-14 Find f(9)

A distributor needs to blend a mix of Gualtemala Antigua coffee that normally sells for $8.50 per pound with a Rift Valley coffe

daser333 [38]

9514 1404 393

Answer:

x+y=70; 8.50x+12.50y=10.56(70)
36 pounds Antigua
34 pounds Rift

Step-by-step explanation:

At the insistence of the problem author, we will let x represent pounds of Antigua coffee and y represent pounds of Rift coffee. Then we have ...

x + y = 70

8.50x +12.50y = 10.56(70) . . . . . total cost of the mix

__

We like to use the variable to represent the high-cost contributor. Here, that is y, so we'll substitute for x:

x = 70-y

8.50(70 -y) +12.50y = 10.56(70)

__

595 +4y = 739.2 . . . . . . . . . . . . . . simplify

4y = 144.2 . . . . . . . . . . . subtract 595

y = 36.05 . . . . . . . divide by 4

x = 70 -36.05 = 33.95

About 36 pounds of Rift Valley coffee and 34 pounds of Gualtemala Antigua coffee must be mixed.

_____

Additional comment

By letting the variable in our equation 8.50(70 -y) +12.50y = 10.56(70) represent the high-cost coffee, we ensure that the simplified equation will have a positive coefficient for the variable. This means we don't have to mess with negative numbers, so eliminating a common source of math errors.

The problem requirement that we use x for the low-cost contributor meant we introduced an extra equation that would not have been needed.

4 0

2 years ago

irena’s boat traveled 76 miles downstream in 4 hours. on the way back it took her 5 hours and 30 minutes to travel 38.5 miles. i

Oxana [17]

Answer:

The speed of the boat in still water is 13 miles/hour.

The speed of the current is 6 miles/hour.

Step-by-step explanation:

Let the speed of the boat in still water be x

And speed of the current be y

When Irena's travelling downstream, the speed of the boat is: