Parallelogram DEFG, DH = x + 3, HF = 3y, GH = 2x – 5, and HE = 5y + 2. Find the values of x and y.

Mathematics

1 answer:

12345 [234]3 years ago

5 0

Your answer is x = 36, y = 13.

We can find this by first realising that DH = HF, and GH = HE, as they are both diagonals of the parallelogram. This allows us to write the equations:

2x - 5 = 5y + 2
x + 3 = 3y

If we rearrange the equation x + 3 = 3y into x = 3y - 3, we can see that this becomes a pair of simultaneous equations that we can solve with substitution. Then we can substitute 3y - 3 into the first equation and solve for y:

2(3y - 3) - 5 = 5y + 2
6y - 6 - 5 = 5y + 2
6y - 11 = 5y + 2
- 5y
y - 11 = 2
+ 11
y = 13

Now because we know that x = 3y - 3, we can substitute 13 into this equation:

x = 3(13) - 3
x = 39 - 3
x = 36

I hope this helps!

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What is the range, min, and max of the function f(x)=13-20x-x²-3x⁴

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Answer:

range: (-∞, 29.4336]
min: -∞
max: 29.4336

Step-by-step explanation:

I found these using a graphing calculator. (See attached)

The function is a polynomial of 4th degree with a negative leading coefficient. (The coefficient of the 4th-degree term is -3.) Therefore, it opens downward and has a range that extends to -∞. This function only has one global maximum and no local minimum.

_____

The maximum can be found by solving the cubic equation that results from taking the derivative of this function and finding the root of that:

df/dx = -12x^3 -2x -20 = 0

There are formulas for the solutions of a cubic, but the one negative real root of this cubic can be found easily with a graphing calculator using iteration:

x ≈ -1.13879908894.

Dividing by -2, the above derivative function can be written as ...

g(x) = 6x^3 +x +10

The one real zero of it can be found using Newton's Method iteration.

The Newton's Method iterator function is

h(x) = x - g(x)/g'(x)

where g'(x) is the derivative of g(x), often available as a function on the graphing calculator.

The starting value for the iteration can be the x-value obtained from the graph: -1.139. It only takes about 2 or 3 iterations to find x to the precision of the calculator: x = h(h(x)). This x is the x-coordinate of the maximum, so f(x) is the maximum value: 29.4335546516.

The attachments show the function definitions and their use for finding the maximum of f(x) using a TI-84 calculator. Y₁ is the function f(x); Y₂ is its derivative, shown above as g(x). Y₃ is the iterating function, shown above as h(x). The nDeriv( ) function is a calculator function that finds the numerical derivative of its argument.