Rotation / reflection question PICTURE INCLUDED

If a/b < c/d with b > 0, d > 0, prove that a+c / b+d lies between the two fractions a/b and c/d .

Tems11 [23]

Divide through everything by b :

$\dfrac{a+c}{b+d} = \dfrac{\dfrac ab + \dfrac cb}{1 + \dfrac db}$

Since a/b < c/d, it follows that

$\dfrac{a+c}{b+d} < \dfrac{\dfrac cd+\dfrac cb}{1 + \dfrac db}$

Multiply through everything on the right side by b/d to get

$\dfrac{a+c}{b+d} < \dfrac{\dfrac{bc}{d^2}+\dfrac cd}{\dfrac bd+1} = \dfrac{\dfrac cd\left(\dfrac bd+1\right)}{\dfrac bd+1} = \dfrac cd$

and so (a + c)/(b + d) < c/d.

For the other side, you can do something similar and divide through everything by d :

$\dfrac{a+c}{b+d} = \dfrac{\dfrac ad + \dfrac cd}{\dfrac bd + 1}$

and a/b < c/d tells us that

$\dfrac{a+c}{b+d} > \dfrac{\dfrac ad + \dfrac ab}{\dfrac bd + 1}$

Then

$\dfrac{a+c}{b+d} > \dfrac{\dfrac ab + \dfrac{ad}{b^2}}{1 + \dfrac db} = \dfrac{\dfrac ab\left(1+\dfrac db\right)}{1 + \dfrac db} = \dfrac ab$

and so (a + c)/(b + d) > a/b.

Then together we get the desired inequality.

5 0

3 years ago

Suppose that the functions s and t are defined for all real numbers x as follows.

jeka94

Answer:

$(s.t)(x) = 4x^2+24x^2\\(s-t)(x) = x+6-4x^2\\(s+t)(-3) = 39$

Step-by-step explanation:

Given functions are:

$s(x)= x+6\\t(x)= 4x^2$

We have to find:

(s.t)(x) => this means we have to multiply the two functions to get the result.

So,

$(s.t)(x) = s(x)*t(x)\\= (x+6)(4x^2)\\=4x^2.x+4x^2.6\\=4x^3+24x^2$

Also we have to find

(s-t)(x) => we have to subtract function t from function s

$(s-t)(x) = s(x) - t(x)\\= (x+6) - (4x^2)\\=x+6-4x^2$

Also we have to find,

(s+t)(-3) => first we have to find sum of both functions and then put -3 in place of x

$(s+t)(x) = s(x)+t(x)\\= x+6+4x^2$

Putting x = -3

$= -3+6+4(-3)^2\\=-3+6+4(9)\\=3+36\\=39$

Hence,

$(s.t)(x) = 4x^2+24x^2\\(s-t)(x) = x+6-4x^2\\(s+t)(-3) = 39$

8 0

3 years ago

A company produces x units of a product per month, where c(x) represents the total cost and r(x) represents the total revenue fo

Nat2105 [25]

Answer:

The total profit P(x) or the month is $P(x)=-0.5x^2+500x-350$ .

Step-by-step explanation:

A company produces x units of a product per month.

The total cost represents by the function C(x).

$C(x)=300x+250$

The total revenue represents by the function R(x).

$R(x)=-0.5x^2+800x-100$

The profit is the difference between revenue and cost.

$P(x)=R(x)-C(x)$

$P(x)=-0.5x^2+800x-100-(300x+250)$

$P(x)=-0.5x^2+800x-100-300x-250$

Combine like terms.

$P(x)=-0.5x^2+(800x-300x)+(-100-250)$

$P(x)=-0.5x^2+500x-350$

Therefore, the total profit P(x) or the month is $P(x)=-0.5x^2+500x-350$ .

5 0

3 years ago

Answer:

C. Robbie's glider

Step-by-step explanation:

P.S -The exact question is -

Given - Melissa and Robbie are flying remote control gliders.

The altitude of Melissa's glider, h(s), in feet, is modeled by this function, where sis time, in seconds, after launch.

m(s) = 0.4(s³ - 11s² + 31s – 1)

The altitude of Robbie's glider is modeled by function r, where sis time, in seconds, after launch.

To find - Which glider reaches the greater maximum altitude in the first 6 seconds after launch?

A. Neither glider reaches a maximum altitude on the given interval.

В. Melissa's glider

C. Robbie's glider

D. Both gliders reach the same altitude on the given interval.

Proof -

At t = 6 sec,

Melisa glider is

h(6) = 0.4((0.6)³ - 11(0.6)² + 31(0.6) – 1)

= 0.4( 0.216 - 3.96 + 18.6 - 1 )

= 0.4(13.856) = 5.5424

⇒h(6) = 5.5424

∴ we get

At t = 6 seconds, Melissa glider is at the altitude of 5.54 feet

Now,

From the figure, we can see that,

At t = 6 seconds, Robbie's glider is approximately at an altitude of 13 feet

Now,

As 13 > 5.5

So,

Robbie's glider is at maximum height in 6 seconds after the launch.

So,

The correct option is - C. Robbie's glider

8 0

3 years ago

Emily's bill for dinner at a restaurant was $61. She left an 18% tip. What was the amount of the tip?

UkoKoshka [18]

You cross multiply. So 61 over 18 = x over 100. You multiply 61 and get the answer of 1600. Now with what you have left, you divide that with 18 and you should get your answer of 338.888889. Make sure to round it to whatever it tells you to round to!

7 0

4 years ago