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2 years ago

If x^2 + xy = 20 and dx/dt = -4 when x = -5 and y = 1, what is dy/dt

Mathematics

1 answer:

SpyIntel [72]2 years ago

7 0

Answer:

3.2

Step-by-step explanation:

x² + xy = 20

Take the derivative with respect to time:

2x dx/dt + x dy/dt + y dx/dt = 20

(2x + y) dx/dt + x dy/dt = 20

Given x = -5, y = 1, and dx/dt = -4:

(2(-5) + 1) (-4) + (-5) dy/dt = 20

(-10 + 1) (-4) − 5 dy/dt = 20

36 − 5 dy/dt = 20

5 dy/dt = 16

dy/dt = 3.2

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two mechanics worked on a car. The first mechanic worked for 10 hours, and the second mechanic worked for 5 hours. Together they

Lerok [7]

Let's make,
mechanic #1's rate = x
mechanic #2's rate = y

* Their rate is dollars per hour ($/hr)

mechanic #1 worked for 20 hours (hr × $/hr = $)
20x = money earned by mech#1

and mechanic #2 worked for 5 hours
5y = money earned by mech#2

together they charged a total of $1150. So the amount of money earned by both mechanics.

20x + 5y = 1150

the sum of the two rates was $95 per hour.

x + y = 95

which means
x = 95 - y

plug (95 - y) in for "x" in the other equation to get everything in terms of one variable.

20(95 - y) + 5y = 1150

solve for y

1900 - 20y + 5y = 1150
1900 - 15y = 1150
-15y = 1150 - 1900
-15y = -750
y = -750/-15
y = 50 $/hr

Now use this to solve for x

x + y = 95
x + 50 = 95
x = 95 - 50
x = 45 $/hr

mech#1 charged 45$/hr
mech #2 charged 50$/hr

7 0

2 years ago

Can someone please help me find the answers to these two questions please?

Sliva [168]

Answer:

Question 13: x = 47°

Question 14: x = 67°

Step-by-step explanation:

Question 13:

add up all the known factors meaning 16, 27 and 90°, then subtract 180 from what you got from adding known factors

Question 14:

out out of all numbers meaning 19, 4 and 90°, then subtract 180 from what you got from adding all known factors

5 0

3 years ago

Two professional baseball teams played a four game series. Attendance for the first three games was 126,503 people, what was the

ioda

Answer: 44,815 people; 126,503 + n = 171,318; n = 171,318 − 126,503

6 0

2 years ago

Math help

inn [45]

You should get photo math you can take a picture and it will give you the answer and show you how to solve it

8 0

2 years ago

Write and equation for the shift of the parent graph y=1/x

SashulF [63]

You can think of this equation as $\bf f(x)=\cfrac{1}{x}\implies f(x)=(x)^{-1}$

and thus apply the transformations to it as such

$\bf \qquad \qquad \qquad \qquad \textit{function transformations}
\\ \quad \\\\
% left side templates
\begin{array}{llll}
f(x)=&{{ A}}({{ B}}x+{{ C}})+{{ D}}
\\ \quad \\
y=&{{ A}}({{ B}}x+{{ C}})+{{ D}}
\\ \quad \\
f(x)=&{{ A}}\sqrt{{{ B}}x+{{ C}}}+{{ D}}
\\ \quad \\
f(x)=&{{ A}}(\mathbb{R})^{{{ B}}x+{{ C}}}+{{ D}}
\\ \quad \\
f(x)=&{{ A}} sin\left({{ B }}x+{{ C}} \right)+{{ D}}
\end{array}\\\\
--------------------\\\\$

$\bf \bullet \textit{ stretches or shrinks horizontally by } {{ A}}\cdot {{ B}}\\\\
\bullet \textit{ flips it upside-down if }{{ A}}\textit{ is negative}
\\\\
\bullet \textit{ horizontal shift by }\frac{{{ C}}}{{{ B}}}\\
\left. \qquad \right. if\ \frac{{{ C}}}{{{ B}}}\textit{ is negative, to the right}\\\\
\left. \qquad \right. if\ \frac{{{ C}}}{{{ B}}}\textit{ is positive, to the left}\\\\$

$\bf \bullet \textit{ vertical shift by }{{ D}}\\
\left. \qquad \right. if\ {{ D}}\textit{ is negative, downwards}\\\\
\left. \qquad \right. if\ {{ D}}\textit{ is positive, upwards}\\\\
\bullet \textit{ period of }\frac{2\pi }{{{ B}}}$

1) D = 2, C = +3

2) D = -12, C = -2

3) C = +6, D = 3

4) C = -7, D = -7

7 0

2 years ago