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2 years ago

14

Find fourth proportional of 6, 9, 18. Please say me correct answer

1 answer:

olganol [36]2 years ago

4 0

A: 3

Good luck on everything

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Penny and Kenny have the same number of football cards.

Pachacha [2.7K]

Hello,
Penny==>a*10 (a is an integer)
Kenny==>b*18 (b is an integer)

a*10=b*18==>a=9*b/5 ==>b=5+n*5
a=9*(5+5*n)/5=9*(1+n)=9+9n
If n=0 then a=9 and b=5 :Number od cards: 9*10=10, 5*18=90
if n=1 then a=19 and b=10: Number of cards: 19*10=190>100 to exclude.

So number of cards=90

7 0

3 years ago

Differentiate with respect to X <br><img src="https://tex.z-dn.net/?f=%20%5Csqrt%7B%20%5Cfrac%7Bcos2x%7D%7B1%20%2Bsin2x%20%7D%20

Mice21 [21]

Power and chain rule (where the power rule kicks in because $\sqrt x=x^{1/2}$ ):

$\left(\sqrt{\dfrac{\cos(2x)}{1+\sin(2x)}}\right)'=\dfrac1{2\sqrt{\frac{\cos(2x)}{1+\sin(2x)}}}\left(\dfrac{\cos(2x)}{1+\sin(2x)}\right)'$

Simplify the leading term as

$\dfrac1{2\sqrt{\frac{\cos(2x)}{1+\sin(2x)}}}=\dfrac{\sqrt{1+\sin(2x)}}{2\sqrt{\cos(2x)}}$

Quotient rule:

$\left(\dfrac{\cos(2x)}{1+\sin(2x)}\right)'=\dfrac{(1+\sin(2x))(\cos(2x))'-\cos(2x)(1+\sin(2x))'}{(1+\sin(2x))^2}$

Chain rule:

$(\cos(2x))'=-\sin(2x)(2x)'=-2\sin(2x)$

$(1+\sin(2x))'=\cos(2x)(2x)'=2\cos(2x)$

Put everything together and simplify:

$\dfrac{\sqrt{1+\sin(2x)}}{2\sqrt{\cos(2x)}}\dfrac{(1+\sin(2x))(-2\sin(2x))-\cos(2x)(2\cos(2x))}{(1+\sin(2x))^2}$

$=\dfrac{\sqrt{1+\sin(2x)}}{2\sqrt{\cos(2x)}}\dfrac{-2\sin(2x)-2\sin^2(2x)-2\cos^2(2x)}{(1+\sin(2x))^2}$

$=\dfrac{\sqrt{1+\sin(2x)}}{2\sqrt{\cos(2x)}}\dfrac{-2\sin(2x)-2}{(1+\sin(2x))^2}$

$=-\dfrac{\sqrt{1+\sin(2x)}}{\sqrt{\cos(2x)}}\dfrac{\sin(2x)+1}{(1+\sin(2x))^2}$

$=-\dfrac{\sqrt{1+\sin(2x)}}{\sqrt{\cos(2x)}}\dfrac1{1+\sin(2x)}$

$=-\dfrac1{\sqrt{\cos(2x)}}\dfrac1{\sqrt{1+\sin(2x)}}$

$=\boxed{-\dfrac1{\sqrt{\cos(2x)(1+\sin(2x))}}}$

5 0

3 years ago

What are the coordinates of the vertex of the table? Is it a minimum or a maximum?

WITCHER [35]

I think the answer is maximum

5 0

3 years ago

Y= 3x+7<br> y = -2x-3<br> What would be the x and y for that solution

alexandr402 [8]

Answer:

So if we are solving for x and y. First we need to subtract both equations. We take each equation and put in parenthesis and subtract.

y-y = (3x+7)-(-2x-3) =

0 = 3x+7+2x+3

0 = 5x+10

-10 = 5x

-2 = x.

Now we need to solve for y.

Plug it in for the first equation. -2*3+7 = -6+7 = 1

Test if we are correct and try in the second equation.

-2*-2-3 = 4-3 = 1

<u>x = -2</u>

<u>y = 1</u>

6 0

3 years ago

Lana took one and a half times as long as jayden to finish a project. If Lana took 15 days, how long did Jayden take ?

aev [14]

10 days. 15 divided by 1.5 is 10

6 0

3 years ago