How do you do this problem

Simplify 4 + (-3) - 2 times (-6)

iVinArrow [24]

Step-by-step explanation:

$= 4 + ( - 3) - 2 ( - 6)$

here ( + ) × ( - ) = ( - )

$= 4 - 3 + 12$

$= 4 + 12 - 3$

$= 16 - 3$

$= 13$

8 0

2 years ago

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Y''+y'+y=0, y(0)=1, y'(0)=0

mars1129 [50]

Answer:

$y=e^{\frac{-t}{2}}\left ( \cos\left ( \frac{\sqrt{3}t}{2} \right )+\frac{1}{\sqrt{3}}\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )$

Step-by-step explanation:

A second order linear , homogeneous ordinary differential equation has form $ay''+by'+cy=0$ .

Given: $y''+y'+y=0$

Let $y=e^{rt}$ be it's solution.

We get,

$\left ( r^2+r+1 \right )e^{rt}=0$

Since $e^{rt}\neq 0$ , $r^2+r+1=0$

{ we know that for equation $ax^2+bx+c=0$ , roots are of form $x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$ }

We get,

$y=\frac{-1\pm \sqrt{1^2-4}}{2}=\frac{-1\pm \sqrt{3}i}{2}$

For two complex roots $r_1=\alpha +i\beta \,,\,r_2=\alpha -i\beta$ , the general solution is of form $y=e^{\alpha t}\left ( c_1\cos \beta t+c_2\sin \beta t \right )$

i.e $y=e^{\frac{-t}{2}}\left ( c_1\cos\left ( \frac{\sqrt{3}t}{2} \right )+c_2\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )$

Applying conditions y(0)=1 on $e^{\frac{-t}{2}}\left ( c_1\cos\left ( \frac{\sqrt{3}t}{2} \right )+c_2\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )$ , $c_1=1$

So, equation becomes $y=e^{\frac{-t}{2}}\left ( \cos\left ( \frac{\sqrt{3}t}{2} \right )+c_2\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )$

On differentiating with respect to t, we get

$y'=\frac{-1}{2}e^{\frac{-t}{2}}\left ( \cos\left ( \frac{\sqrt{3}t}{2} \right )+c_2\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )+e^{\frac{-t}{2}}\left ( \frac{-\sqrt{3}}{2} \sin \left ( \frac{\sqrt{3}t}{2} \right )+c_2\frac{\sqrt{3}}{2}\cos\left ( \frac{\sqrt{3}t}{2} \right )\right )$

Applying condition: y'(0)=0, we get $0=\frac{-1}{2}+\frac{\sqrt{3}}{2}c_2\Rightarrow c_2=\frac{1}{\sqrt{3}}$

Therefore,

$y=e^{\frac{-t}{2}}\left ( \cos\left ( \frac{\sqrt{3}t}{2} \right )+\frac{1}{\sqrt{3}}\sin \left ( \frac{\sqrt{3}t}{2} \right ) \right )$

3 0

3 years ago

How many positive integer factors of 100! are multiples of 2 or 3?

elena-s [515]

Positive integer factors of 100:

1, 2, 4, 5, 10, 20, 25, 50, 100

Now find if they are a multiple of 2 or 3.

2, 4, 10, 20, 50, 100

That is 6 factors.

3 0

4 years ago

A 18 foot ladder is leaning against a wall as shown

Inga [223]

I'm guessing the diagram shows a ladder leaning against a wall, making a right angle triangle with respect to the ground and the wall.

So, the wall's height is going to be the 'h', which will also be the 'opposite side' from the angle ϴ which is made from the ladder and the ground.
The ladder's length (18 foot) is going to be the 'hypotenuse' side and the other remaining side will be the 'adjacent'.

Now, once you've sorted out which side is which, we have to find the h (opp), and according to SOH CAH TOA, we will choose Sinϴ = opp/hyp.
so Sinϴ = h/18....now we gotta find h, so 'cross multiply' the equation to get h = 18 x sinϴ.

To find angle ϴ, simply take the inverse of Sinϴ= h/18... and you'll get ϴ = sin-1 (sin inverse) h/18

Hope this helps

6 0

3 years ago

Peter bought 8 lemons for $6 What was the cost for 1 lemon?

Alexeev081 [22]

$1.3 per lemon. I divided 8 by $6 and got 1.3.

3 0

3 years ago

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