Respuesta :
Answer: (x, y, z) = (-3, 2, 4)
In other words, x = -3, y = 2 and z = 4.
You'll enter the number only into each box.
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Explanation:
There are a few routes we can take to solve this. I'll use substitution.
First let's isolate y in the second equation.
2x - y + 3z = 4
2x + 3z = 4+y
4+y = 2x+3z
y = 2x+3z-4
This is then plugged into the first equation
3x+2y+4z = 11
3x+2( y )+4z = 11
3x+2( 2x+3z-4)+4z = 11 .... replace y with 2x+3z-4; since y = 2x+3z-4
3x+4x+6z-8+4z =11
7x+10z-8 = 11
7x+10z = 11+8
7x+10z = 19 .... we'll call this equation (4) and come back to this later
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Move onto the third equation (of the original equations given)
Plug in y = 2x+3z-4
5x - 3y + 5z = -1
5x - 3( y ) + 5z = -1
5x - 3( 2x+3z-4 ) + 5z = -1
5x - 6x - 9z + 12 + 5z = -1
-x - 4z + 12 = -1
-x - 4z = -1-12
-x - 4z = -13 ..... let's call this equation (5)
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To recap, we found equation (4) and equation (5) to be
- 7x+10z = 19
- -x - 4z = -13
We can then solve for x in equation (5) like so
-x - 4z = -13
-x = -13 + 4z
-x = 4z - 13
x = -(4z - 13)
x = -4z + 13
This is then plugged into equation (4)
7x+10z = 19
7(-4z+13)+10z = 19 .... note how we now have one variable
-28z+91+10z = 19
-18z+91 = 19
-18z = 19-91
-18z = -72
z = -72/(-18)
z = 4
We can use this value of z to find x
x = -4z+13
x = -4(4)+13
x = -16+13
x = -3
Use the values of x and z to find y. We'll revisit the first equation in which we isolated y
y = 2x+3z-4
y = 2(-3)+3(4)-4
y = -6+12-4
y = 6-4
y = 2
So overall, the solution to this system is (x, y, z) = (-3, 2, 4)
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Checking the answer:
We'll replace x,y,z with the values we found.
- In the first equation, 3x+2y+4z = 11 becomes 3(-3)+2(2)+4(4) = 11 and that simplifies to 11 = 11. In other words, the expression 3(-3)+2(2)+4(4) turns into 11. This confirms the first equation.
- Repeat the same idea for the second equation. We have 2x-y+3z=4 turn into 2(-3)-2+3(4) = 4 and that simplifies to 4 = 4. The answer is verified here.
- The third equation 5x-3y+5z = -1 becomes 5(-3)-3(2)+5(4) = -1 which simplifies to -1 = -1. We get a true equation here as well.
Since all three equations are true when (x, y, z) = (-3, 2, 4), this verifies the answer completely. This is the only solution to the system. The system is independent and consistent.
