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3 years ago

8x + y = -39 2x - 5y = 27 Solve the system by elimination

Mathematics

1 answer:

Ahat [919]3 years ago

5 0

Answer:

(-4, -7)

Step-by-step explanation:

21y=-147

y=-7

2x-5x(-7)=27

x=-4

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Solve the following pairs of simultaneous equations

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$x + 3y = 14|\cdot(-3)\\3x + y = 10\\\\-3x - 9y = -42\\3x + y = 10\\\\-8y = -32 => y = 4, x = 14 - 12 = 2\\(2, 4)$

$5x + y = 27|\cdot(-3)\\4x + 3y = 26\\\\-15x - 3y = -81\\4x + 3y = 26\\\\-11x = - 55 => x=5, y = 27-25 = 2\\(5, 2)$

$-6x + 5y = -14\\-2x + y = -6| \cdot(-3)\\\\-6x + 5y = -14\\6x - 3y = 18\\\\2y = 4 => y = 2, x = -1/2\cdot(-6 -2) = 4\\(4, 2)$

$2x + 5y = 14\\3x + y = -5|\cdot(-5)\\\\2x + 5y = 14\\-15x - 5y = 25\\\\-13x = 39 => x = -3, y = 1/5\cdot(14 - 2(-3)) = 4\\(-3, 4)$

$-3x + 2y = 6\\x + 4y = -9|\cdot3\\\\-3x + 2y = 6\\3x + 12y = -27\\\\14y = -21 => y = -\frac{3}{2}, x = -3\\(-3, -1.5)$

$3x - 5y = 7\\x + y = -11|\cdot(5)\\\\3x - 5y = 7\\5x + 5y = -55\\\\8x = -48=> x= -6, y = -11 + 6 = -5\\(-6, -5)$

$2x + 3y = 9|\cdot(-2)\\4x + y = -7\\\\-4x - 6y = -18\\4x + y = -7\\\\-5y = -25 => y = 5, x = 1/4(-7-5) = -3\\(-3, 5)$

$-x + 5y = 7|\cdot(-1)\\5x + 5y = 19\\\\x-5y = -7\\5x + 5y = 19\\\\6x = 12 => x = 2, y = (7 + 2)/5 = \frac{9}{5}\\(2, 1.8)$

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3 years ago

If you add 21 to my number and then multiply the result by 3, you will get 84 more than two-thirds of my number. Find my number.

Ksivusya [100]

Based on the calculations, the unknown number is equal to $\frac{-45}{7}$

Let the unknown number be x.

<h3>How to find an unknown number:</h3>

Translate the word problem into an algebraic expression, we have;

Adding 21 to the unknown number:

$21 +x$

Multiplying the result by 3:

$3\times (21+x)$

84 more than two-thirds of the unknown number:

$\frac{2x}{3} +84$

Equating the equations, we have:

$3\times (21+x) = \frac{2x}{3} +84\\\\43+3x=\frac{2x}{3} +84$

Cross-multiplying, we have:

$43+3x=\frac{2x}{3} +84\\\\129+9x=2x+84\\\\9x-2x=84-129\\\\7x=-45\\\\x=\frac{-45}{7}$

Read more on word problems here: brainly.com/question/13170908

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