Answer: The required expression is,
$ 40(0.85)
Step-by-step explanation:
Given,
The original cost of the videogame = $ 40,
Discount percentage = 15%,
So, the amount of discount = 15% of 40
= (0.15)40 ( ∵ 1% = 0.01 )
Hence, the cost of the videogame = original cost - discount
= 40 - (0.15)40
= 40 (1-0.15)
= 40(0.85)
Which is the required expression .
You can solve this in two ways.
1. Graphical. Plot the graph for x between -5 and 1 (see attachement).
The vertex of the graph is the peak of the curve, which has the coordinates x=-2, y=-9.
2. Analytical. Calculate the derivative of the function f(x)

Solve the equation:

will give the solution x=-2.
Replace x=-2 in the f(x) function and you'll get the value of y:

You get the same answer: x=-2, y=-9
So the answer is
<span>B. (-2, -9)</span>
Answer: cookbook $40 and science $15
Step-by-step explanation:
So x + y = 45, and 4x + 5y = 195. Get y by itself. Subtract x from both sides in the first equation to get y = 45 -x, and subtract 4x from the second equation to get 5y = 195 - 4x. Divide by 5 to both sides to get y = 39 - 4/5x. 39 - 4/5x = 45 - x. Add x to both sides to get 39 - 1/5x = 45. Subtract 39 from both sides to get -1/5x = 6. Divide by -1/5 to get x = -30, or 30. In the first equation, do 30 + y = 45. Subtract 30 from both sides to get y = 15. Check. 4(30) + 15(5) = 195, or 120 + 75 = 195.