How do i solve the linear system -14x+15y=15 21x-20y=-10 using elimination

Mathematics

1 answer:

valina [46]3 years ago

4 0

Solve the following system using elimination:
{15 y - 14 x = 15 | (equation 1)
{21 x - 20 y = -10 | (equation 2)

Swap equation 1 with equation 2:
{21 x - 20 y = -10 | (equation 1)
{-(14 x) + 15 y = 15 | (equation 2)

Add 2/3 × (equation 1) to equation 2:
{21 x - 20 y = -10 | (equation 1)
{0 x+(5 y)/3 = 25/3 | (equation 2)

Multiply equation 2 by 3/5:
{21 x - 20 y = -10 | (equation 1)
{0 x+y = 5 | (equation 2)

Add 20 × (equation 2) to equation 1:
{21 x+0 y = 90 | (equation 1)
{0 x+y = 5 | (equation 2)

Divide equation 1 by 21:
{x+0 y = 30/7 | (equation 1)
{0 x+y = 5 | (equation 2)

Collect results:

Answer: {x = 30/7, y = 5

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Evaluate the line integral, where c is the given curve. (x + 9y) dx + x2 dy, c c consists of line segments from (0, 0) to (9, 1)

viktelen [127]

$\displaystyle\int_C(x+9y)\,\mathrm dx+x^2\,\mathrm dy=\int_C\langle x+9y,x^2\rangle\cdot\underbrace{\langle\mathrm dx,\mathrm dy\rangle}_{\mathrm d\mathbf r}$

The first line segment can be parameterized by $\mathbf r_1(t)=\langle0,0\rangle(1-t)+\langle9,1\rangle t=\langle9t,t\rangle$ with $0\le t\le1$ . Denote this first segment by $C_1$ . Then

$\displaystyle\int_{C_1}\langle x+9y,x^2\rangle\cdot\mathbf dr_1=\int_{t=0}^{t=1}\langle9t+9t,81t^2\rangle\cdot\langle9,1\rangle\,\mathrm dt$
$=\displaystyle\int_0^1(162t+81t^2)\,\mathrm dt$
$=108$

The second line segment ( $C_2$ ) can be described by $\mathbf r_2(t)=\langle9,1\rangle(1-t)+\langle10,0\rangle t=\langle9+t,1-t\rangle$ , again with $0\le t\le1$ . Then

$\displaystyle\int_{C_2}\langle x+9y,x^2\rangle\cdot\mathrm d\mathbf r_2=\int_{t=0}^{t=1}\langle9+t+9-9t,(9+t)^2\rangle\cdot\langle1,-1\rangle\,\mathrm dt$
$=\displaystyle\int_0^1(18-8t-(9+t)^2)\,\mathrm dt$
$=-\dfrac{229}3$

Finally,

$\displaystyle\int_C(x+9y)\,\mathrm dx+x^2\,\mathrm dy=108-\dfrac{229}3=\dfrac{95}3$

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4 years ago

Find angles A, B, C, D, & E.

matrenka [14]

Answer:

Step-by-step explanation:

B = 35 {Alternate interior angles}

C = 75 {Corresponding angles}

D + 75 = 180 {Linear pair}

D = 180 - 75

D = 105

A = C {Corresponding angles}