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3 years ago

10

-4 + -7 (-2) =? Minus equations always give me trouble :/

2 answers:

USPshnik [31]3 years ago

8 0

<span>-4 + -7 (-2)
= -4 + 14 (a negative multiplies a negative equal positive)
= 10</span>

steposvetlana [31]3 years ago

6 0

The answer is 10.
-4+(-7)(-2)=
-4+14=
10

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Find all the solutions for the equation:

Contact [7]

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

Divide both sides by $x^2\,\mathrm dx$ to get

$2\left(\dfrac yx\right)^2-\left(1+\dfrac yx\right)^2\dfrac{\mathrm dy}{\mathrm dx}=0$

$\dfrac{\mathrm dy}{\mathrm dx}=\dfrac{2\left(\frac yx\right)^2}{\left(1+\frac yx\right)^2}$

Substitute $v(x)=\dfrac{y(x)}x$ , so that $\dfrac{\mathrm dv(x)}{\mathrm dx}=\dfrac{x\frac{\mathrm dy(x)}{\mathrm dx}-y(x)}{x^2}$ . Then

$x\dfrac{\mathrm dv}{\mathrm dx}+v=\dfrac{2v^2}{(1+v)^2}$

$x\dfrac{\mathrm dv}{\mathrm dx}=\dfrac{2v^2-v(1+v)^2}{(1+v)^2}$

$x\dfrac{\mathrm dv}{\mathrm dx}=-\dfrac{v(1+v^2)}{(1+v)^2}$

The remaining ODE is separable. Separating the variables gives

$\dfrac{(1+v)^2}{v(1+v^2)}\,\mathrm dv=-\dfrac{\mathrm dx}x$

Integrate both sides. On the left, split up the integrand into partial fractions.

$\dfrac{(1+v)^2}{v(1+v^2)}=\dfrac{v^2+2v+1}{v(v^2+1)}=\dfrac av+\dfrac{bv+c}{v^2+1}$

$\implies v^2+2v+1=a(v^2+1)+(bv+c)v$

$\implies v^2+2v+1=(a+b)v^2+cv+a$

$\implies a=1,b=0,c=2$

Then

$\displaystyle\int\frac{(1+v)^2}{v(1+v^2)}\,\mathrm dv=\int\left(\frac1v+\frac2{v^2+1}\right)\,\mathrm dv=\ln|v|+2\tan^{-1}v$

On the right, we have

$\displaystyle-\int\frac{\mathrm dx}x=-\ln|x|+C$

Solving for $v(x)$ explicitly is unlikely to succeed, so we leave the solution in implicit form,

$\ln|v(x)|+2\tan^{-1}v(x)=-\ln|x|+C$

and finally solve in terms of $y(x)$ by replacing $v(x)=\dfrac{y(x)}x$ :

$\ln\left|\frac{y(x)}x\right|+2\tan^{-1}\dfrac{y(x)}x=-\ln|x|+C$

$\ln|y(x)|-\ln|x|+2\tan^{-1}\dfrac{y(x)}x=-\ln|x|+C$

$\boxed{\ln|y(x)|+2\tan^{-1}\dfrac{y(x)}x=C}$

7 0

3 years ago

–20 ÷ 5 = <br><br> I need help

Rashid [163]

The answer is -4
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7 0

3 years ago

X^3-13x^2+40x=0 quadratic

lutik1710 [3]

Answer:

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or

x=5

x=8

Step-by-step explanation:

x(x^2-13x+40)
x(x-5) (x-8)

6 0

3 years ago

What is the equation of the line perpendicular to y=2x+3.14 going through the points (2,4)?

inessss [21]

Answer:

$x+2y-10=0$

Step-by-step explanation:

Consider an equation: $y=mx+c$

Here, m is the slope of the line and c is the y-intercept.

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Here, slope is $m=2$

As product of slopes of two perpendicular lines is equal to $-1$ , slope of the required line is $m_1=\frac{-1}{m}=\frac{-1}{2}$ .

Let $(x_1,y_1)=(2,4)$

Equation of the required line is $y-y_1=m_1(x-x_1)$

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8 0

3 years ago

Write an integer to represent the situation: to grow six inches *

Naddika [18.5K]

Answer:

(+)6

Step-by-step explanation:

Grow means it will be positive and 6 means it will be, well, 6

6 0

3 years ago

Read 2 more answers