There are 294 boys and 322 girls in the hill school. how many students are in the school.

The notation f:S→T denotes that f is a function, also called a map , defined on all of a set S and whose outputs lie in a set T

AnnyKZ [126]

Answer:

There are many. Two examples are

$f(x) = x, \\f(x) = x^3$

Step-by-step explanation:

There are many examples. The simplest is

1 -

$f(x) = x$

It is trivial that

$\text{if \,\,\,\,} f(x) = f(y) \,\,\,\,\,\text{then} \,\,\,\,\, x=y$

2 -

$f(x) = x^3$

That function is injective as well.

$\text{if \,\,\,\,} x^3 = y^3 \,\,\,\,\,\text{then} \,\,\,\,\, x=y$

An example of a function that is NOT injective is

$f(x) = x^2$

Notice that

$f(-2) = (-2)^2 = 2^2 = 4$

4 0

3 years ago

Solve the following differential equations using classical methods. Assume zero initial conditions.

MA_775_DIABLO [31]

I'll use the integrating factor method for the first DE, and undetermined coefficients for the second one.

(a) Multiply both sides by exp(7t ):

exp(7t ) dx/dt + 7 exp(7t ) x = 5 exp(7t ) cos(2t )

The left side is now the derivative of a product:

d/dt [exp(7t ) x] = 5 exp(7t ) cos(2t )

Integrate both sides:

exp(7t ) x = 10/53 exp(7t ) sin(2t ) + 35/53 exp(7t ) cos(2t ) + C

Solve for x :

x = 10/53 sin(2t ) + 35/53 cos(2t ) + C exp(-7t )

(b) Solve the corresonding homogeneous DE:

d²x/dt ² + 6 dx/dt + 8x = 0

has characteristic equation

r ² + 6r + 8 = (r + 4) (r + 2) = 0

with roots at r = -4 and r = -2. So the characteristic solution is

x (char.) = C₁ exp(-4t ) + C₂ exp(-2t )

For the particular solution, assume an ansatz of the form

x (part.) = a cos(3t ) + b sin(3t )

with derivatives

dx/dt = -3a sin(3t ) + 3b cos(3t )

d²x/dt ² = -9a cos(3t ) - 9b sin(3t )

Substitute these into the non-homogeneous DE and solve for the coefficients:

(-9a cos(3t ) - 9b sin(3t ))

… + 6 (-3a sin(3t ) + 3b cos(3t ))

… + 8 (a cos(3t ) + b sin(3t ))

= (-a + 18b) cos(3t ) + (-18a - b) sin(3t ) = 5 sin(3t )

So we have

-a + 18b = 0

-18a - b = 5

==> a = -18/65 and b = -1/65

so that the particular solution is

x (part.) = -18/65 cos(3t ) - 1/65 sin(3t )

and thus the general solution is

x (gen.) = x (char.) + x (part.)

x = C₁ exp(-4t ) + C₂ exp(-2t ) - 18/65 cos(3t ) - 1/65 sin(3t )

7 0

3 years ago

Lisa has eight less than triple the number of nail polish bottles as Flo. Lisa has 13 nail polish bottles.

iVinArrow [24]

It's C. because 3n -8 is the minus 8 that Liza has so it = 13

3 0

3 years ago

For the inverse variation equation xy = k, what is the constant of variation, k, when x = 7 and y = 3?

Artyom0805 [142]

Answer:

k=21

Step-by-step explanation:

x=7 X y=3 = 21

7 x 3 = 21

3 0

3 years ago

Read 2 more answers

A new car is purchased for 16500 dollars. The value of the car depreciates at 5.75% per year. What will the value of the car be,

Gnom [1K]

A=16500(1-0.0575)^5
A=16,500×(1−0.0575)^(5)
A=12,271.30

7 0

3 years ago