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2 years ago

Solve the system of equations. 7x−3y=20 y=5x−4 x= y=

Mathematics

2 answers:

drek231 [11]2 years ago

8 0

Answer:

x = -1, and y = -9

Step-by-step explanation:

This is done by solving one of the two equations for x or y, then substituting it in place of that variable in the other equation.

Since y is already clearly defined in the second equation let's go with that:

$Given\ 7x - 3y = 20,\ and\ y = 5x - 4$

$7x - 3(5x - 4) = 20$

$7x - 15x + 12 = 20$

$7x - 15x = 20 - 12$

$-8x = 8$

$x = -1$

Now we can replace x in the equation for y with -1:

$y = 5(-1) - 4$

$y = -5 - 4$

$y = -9$

To make sure our answers are correct, let's substitute them into the original equations:

$(-9) = 5(-1) - 4\\-9 = -5 - 4\\-9 = -9$

Good, let's test the other equation

$7(-1) - 3(-9) = 20\\-7 - (-27) = 20\\-7 + 27 = 20\\20 = 20$

So we know that our answer is correct.

Ksenya-84 [330]2 years ago

5 0

Answer:

Step-by-step explanation:

substitute the value of y in the first equation.

7x-3(5x-4)=20

7x-15x+12=20

-8x=20-12

x=8/-8

x= -1

then you substitute the value of x on the y equation to find y

y=5×-1 -4

y= -5-4

y= -9

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