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oksian1 [2.3K]
3 years ago
15

Y is directly proportional to the square of x.

Mathematics
1 answer:
RUDIKE [14]3 years ago
5 0

Answer:

The value of y is 847 for x=11

Step-by-step explanation:

It is given that y is directly proportional to the square of x

This can be written mathematically as:

y \propto  x^2

Removing the proportionality symbol introduces a proportionality constant in the equation which is denoted by k

y = kx^2

Given that "When x is 5, y is 175"

175 = k (5)^2\\175 = k*25\\k = \frac{175}{25}\\k = 7

Putting the value of k

y = 7x^2

Now putting x = 11

y = 7(11)^2\\y = 7 * 121\\y = 847

Hence,

The value of y is 847 for x=11

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<img src="https://tex.z-dn.net/?f=log_%7B8%20x%5E%7B2%7D%20-23x%2B15%7D%282x-2%29%20%5Cleq%200" id="TexFormula1" title="log_{8 x
grandymaker [24]
\log_{8x^2-23x+15} (2x-2) \leq 0

The domain:
The number of which the logarithm is taken must be greater than 0.
2x-2 \ \textgreater \  0 \\&#10;2x\ \textgreater \ 2 \\&#10;x\ \textgreater \ 1 \\ x \in (1, +\infty)

The base of the logarithm must be greater than 0 and not equal to 1.
* greater than 0:
8x^2-23x+15\ \textgreater \ 0 \\ 8x^2-8x-15x+15\ \textgreater \ 0 \\ 8x(x-1)-15(x-1)\ \textgreater \ 0 \\ (8x-15)(x-1)\ \textgreater \ 0 \\ \\ \hbox{the zeros:} \\ 8x-15=0 \ \lor \ x-1=0 \\ 8x=15 \ \lor \ x=1 \\ x=\frac{15}{8} \\ x=1 \frac{7}{8} \\ \\&#10;\hbox{the coefficient of } x^2 \hbox{ is greater than 0 so the parabola op} \hbox{ens upwards} \\&#10;\hbox{the values greater than 0 are between } \pm \infty \hbox{ and the zeros} \\ \\&#10;x \in (-\infty, 1) \cup (1 \frac{7}{8}, +\infty)

*not equal to 1:
8x^2-23x+15 \not= 1 \\&#10;8x^2-23x+14 \not= 0 \\&#10;8x^2-16x-7x+14 \not= 0 \\&#10;8x(x-2)-7(x-2) \not= 0 \\&#10;(8x-7)(x-2) \not= 0 \\&#10;8x-7 \not=0 \ \land \ x-2 \not= 0 \\&#10;8x \not= 7 \ \land \ x \not= 2 \\&#10;x \not= \frac{7}{8} \\ x \notin \{\frac{7}{8}, 2 \}

Sum up all the domain restrictions:
x \in (1, +\infty) \ \land \ x \in (-\infty, 1) \cup (1 \frac{7}{8}, +\infty) \ \land \ x \notin \{ \frac{7}{8}, 2 \} \\ \Downarrow \\&#10;x \in (1 \frac{7}{8}, 2) \cup (2, +\infty)&#10;

The solution:
\log_{8x^2-23x+15} (2x-2) \leq 0 \\ \\&#10;\overline{\hbox{convert 0 to the logarithm to base } 8x^2-23x+15} \\&#10;\Downarrow \\&#10;\underline{(8x^2-23x+15)^0=1 \hbox{ so } 0=\log_{8x^2-23x+15} 1 \ \ \ \ \ \ \ }&#10;\\ \\&#10;\log_{8x^2-23x+15} (2x-2) \leq \log_{8x^2-23x+15} 1

Now if the base of the logarithm is less than 1, then you need to flip the sign when solving the inequality. If it's greater than 1, the sign remains the same.

* if the base is less than 1:
 8x^2-23x+15 \ \textless \  1 \\&#10;8x^2-23x+14 \ \textless \  0 \\ \\&#10;\hbox{the zeros have already been calculated: they are } x=\frac{7}{8} \hbox{ and } x=2 \\&#10;\hbox{the coefficient of } x^2 \hbox{ is greater than 0 so the parabola ope} \hbox{ns upwards} \\&#10;\hbox{the values less than 0 are between the zeros} \\ \\&#10;x \in (\frac{7}{8}, 2) \\ \\&#10;\hbox{including the domain:} \\&#10;x \in (\frac{7}{8}, 2) \ \land \ x \in (1 \frac{7}{8}, 2) \cup (2, +\infty) \\ \Downarrow \\ x \in (1 \frac{7}{8} , 2)

The inequality:
\log_{8x^2-23x+15} (2x-2) \leq \log_{8x^2-23x+15} 1 \ \ \ \ \ \ \ |\hbox{flip the sign} \\ 2x-2 \geq 1 \\ 2x \geq 3 \\ x \geq \frac{3}{2} \\ x \geq 1 \frac{1}{2} \\ x \in [1 \frac{1}{2}, +\infty) \\ \\ \hbox{including the condition that the base is less than 1:} \\ x \in [1 \frac{1}{2}, +\infty) \ \land \x \in (1 \frac{7}{8} , 2) \\ \Downarrow \\ x \in (1 \frac{7}{8}, 2)

* if the base is greater than 1:
8x^2-23x+15 \ \textgreater \ 1 \\ 8x^2-23x+14 \ \textgreater \ 0 \\ \\ \hbox{the zeros have already been calculated: they are } x=\frac{7}{8} \hbox{ and } x=2 \\ \hbox{the coefficient of } x^2 \hbox{ is greater than 0 so the parabola ope} \hbox{ns upwards} \\ \hbox{the values greater than 0 are between } \pm \infty \hbox{ and the zeros}

x \in (-\infty, \frac{7}{8}) \cup (2, +\infty) \\ \\ \hbox{including the domain:} \\ x \in (-\infty, \frac{7}{8}) \cup (2, +\infty) \ \land \ x \in (1 \frac{7}{8}, 2) \cup (2, +\infty) \\ \Downarrow \\ x \in (2, \infty)

The inequality:
\log_{8x^2-23x+15} (2x-2) \leq \log_{8x^2-23x+15} 1 \ \ \ \ \ \ \ |\hbox{the sign remains the same} \\ 2x-2 \leq 1 \\ 2x \leq 3 \\ x \leq \frac{3}{2} \\ x \leq 1 \frac{1}{2} \\ x \in (-\infty, 1 \frac{1}{2}] \\ \\ \hbox{including the condition that the base is greater than 1:} \\ x \in (-\infty, 1 \frac{1}{2}] \ \land \ x \in (2, \infty) \\ \Downarrow \\ x \in \emptyset

Sum up both solutions:
x \in (1 \frac{7}{8}, 2) \ \lor \ x \in \emptyset \\ \Downarrow \\&#10;x \in (1 \frac{7}{8}, 2)

The final answer is:
\boxed{x \in (1 \frac{7}{8}, 2)}
5 0
3 years ago
For the given expression, use the Commutative Property of Addition to enter an equivalent expression.
Triss [41]

Answer:

x+19=19+x

Step-by-step explanation:

3 0
3 years ago
Bus A and Bus B leave the bus depot at 8 am.
LenaWriter [7]

Answer: 10:55

Step-by-step explanation:

Taking statement at face value and the simplest scenario that commencing from 08:00am the buses take a route from depot that returns bus A to depot at 25min intervals while Bus B returns at 35min intervals.

The time the buses will be back at the depot simultaneously will be when:

N(a) * 25mins = N(b) * 35mins

Therefore, when N(b) * 35 is divisible by 25 where N(a) and N(b) are integers.

Multiples of 25 (Bus A) = 25, 50, 75, 100, 125, 150, 175, 200 etc

Multiples of 35 (Bus B) = 35, 70, 105, 140, 175, 210, 245 etc

This shows that after 7 circuits by BUS A and 5 circuits by Bus B, there will be an equal number which is 175 minutes.

So both buses are next at Depot together after 175minutes (2hr 55min) on the clock that is

at 08:00 + 2:55 = 10:55

6 0
3 years ago
On a cold days, Leah likes to make hot chocolate. She uses 8 tablespoons of cocoa and 2 tablespoons of sugar. Leah double the re
Tju [1.3M]

Answer:

4 tbsp

Step-by-step explanation:

5 0
3 years ago
Read 2 more answers
HELP ASAP WILL MAEK BRAINLIEST Find the volume of this rectangular pyramid. Also do the correct unit ex- cm, cm^2 cm^3
pav-90 [236]

Answer:

162 cm^3

Step-by-step explanation:

Volume of a rectangular pyramid is given as = \frac{1}{3}lwh

Where,

l = 9 cm

w = 6 cm

h = 9 cm

Plug in the above values into the formula for volume of rectangular pyramid:

Volume = \frac{1}{3}*9*6*9

Volume = 3*6*9

Volume =  162 cm^3

Volume of the rectangular pyramid = 162 cm^3

4 0
4 years ago
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