Ask question

Ask question

All categories

2 years ago

8

4. (i) Solve the equation 2x2 – 7x + 4 = 0, giving

1 answer:

Colt1911 [192]2 years ago

6 0

????????????????????????????Step-by-step explanation:

You might be interested in

(X^2+y^2+x)dx+xydy=0<br> Solve for general solution

aksik [14]

Check if the equation is exact, which happens for ODEs of the form

$M(x,y)\,\mathrm dx+N(x,y)\,\mathrm dy=0$

if $\frac{\partial M}{\partial y}=\frac{\partial N}{\partial x}$ .

We have

$M(x,y)=x^2+y^2+x\implies\dfrac{\partial M}{\partial y}=2y$

$N(x,y)=xy\implies\dfrac{\partial N}{\partial x}=y$

so the ODE is not quite exact, but we can find an integrating factor $\mu(x,y)$ so that

$\mu(x,y)M(x,y)\,\mathrm dx+\mu(x,y)N(x,y)\,\mathrm dy=0$

<em>is</em> exact, which would require

$\dfrac{\partial(\mu M)}{\partial y}=\dfrac{\partial(\mu N)}{\partial x}\implies \dfrac{\partial\mu}{\partial y}M+\mu\dfrac{\partial M}{\partial y}=\dfrac{\partial\mu}{\partial x}N+\mu\dfrac{\partial N}{\partial x}$

$\implies\mu\left(\dfrac{\partial N}{\partial x}-\dfrac{\partial M}{\partial y}\right)=M\dfrac{\partial\mu}{\partial y}-N\dfrac{\partial\mu}{\partial x}$

Notice that

$\dfrac{\partial N}{\partial x}-\dfrac{\partial M}{\partial y}=y-2y=-y$

is independent of <em>x</em>, and dividing this by $N(x,y)=xy$ gives an expression independent of <em>y</em>. If we assume $\mu=\mu(x)$ is a function of <em>x</em> alone, then $\frac{\partial\mu}{\partial y}=0$ , and the partial differential equation above gives

$-\mu y=-xy\dfrac{\mathrm d\mu}{\mathrm dx}$

which is separable and we can solve for $\mu$ easily.

$-\mu=-x\dfrac{\mathrm d\mu}{\mathrm dx}$

$\dfrac{\mathrm d\mu}\mu=\dfrac{\mathrm dx}x$

$\ln|\mu|=\ln|x|$

$\implies \mu=x$

So, multiply the original ODE by <em>x</em> on both sides:

$(x^3+xy^2+x^2)\,\mathrm dx+x^2y\,\mathrm dy=0$

Now

$\dfrac{\partial(x^3+xy^2+x^2)}{\partial y}=2xy$

$\dfrac{\partial(x^2y)}{\partial x}=2xy$

so the modified ODE is exact.

Now we look for a solution of the form $F(x,y)=C$ , with differential

$\mathrm dF=\dfrac{\partial F}{\partial x}\,\mathrm dx+\dfrac{\partial F}{\partial y}\,\mathrm dy=0$

The solution <em>F</em> satisfies

$\dfrac{\partial F}{\partial x}=x^3+xy^2+x^2$

$\dfrac{\partial F}{\partial y}=x^2y$

Integrating both sides of the first equation with respect to <em>x</em> gives

$F(x,y)=\dfrac{x^4}4+\dfrac{x^2y^2}2+\dfrac{x^3}3+f(y)$

Differentiating both sides with respect to <em>y</em> gives

$\dfrac{\partial F}{\partial y}=x^2y+\dfrac{\mathrm df}{\mathrm dy}=x^2y$

$\implies\dfrac{\mathrm df}{\mathrm dy}=0\implies f(y)=C$

So the solution to the ODE is

$F(x,y)=C\iff \dfrac{x^4}4+\dfrac{x^2y^2}2+\dfrac{x^3}3+C=C$

$\implies\boxed{\dfrac{x^4}4+\dfrac{x^2y^2}2+\dfrac{x^3}3=C}$

5 0

3 years ago

Logan drove from New Orleans to Nashville to visit friends. Logan drove the speed

Nata [24]

Answer:

540 miles

Step-by-step explanation:

60 miles per 1 hour

120 per 2 hours... etc.

multiply 60 and 9 to get 540

7 0

3 years ago

Find the slope of this graph <br> Pls help i cant get anyone to help me

guajiro [1.7K]

Answer:

Slope is 1

Step-by-step explanation:

7 0

2 years ago

Read 2 more answers

A peice of fabric costs $5.29 a yard which is an estimated cost of 16.3 yards of fabric?

DerKrebs [107]

Answer:

90

Step-by-step explanation:

$5.29 * 16.3 = $86.227

=$86.23

86.23 could be rounded up to 90

6 0

3 years ago

Consider the rectangle enlargement. Pls answer the three questions I will mark brainliest!!

Alenkasestr [34]

Answer:

Perimeter of the original Rectangle is

2(4.5+4.3)=2×8.8= <u>17.6</u><u> </u><u>mm</u>

Side length of the enlarged rectangle is

$\frac{4.5}{4.3} = \frac{24.3}{x} \\ x = \frac{24.3 \times 4.3}{4.5} \\ \boxed{x = 23.22 \: mm}$

Perimeter of the enlarged rectangle

2(24.3+23.22)= 2×47.52= <u>95.04 mm</u>

7 0

2 years ago