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Question
Math
Posted 9 months ago

Problem 1. (10 points)
Linear System - Three Variables
Solve the following system of equations using Gaussian elimination method. If there are no solutions, type "N" for both x,yx, y and zz. If there are infinitely many solutions, type " zz " for zz, and expressions in terms of zz for xx and yy.
4x3y5z=43x+1y8z=15x+1y+6z=3
\begin{aligned}
4 x-3 y-5 z & =-4 \\
3 x+1 y-8 z & =-1 \\
-5 x+1 y+6 z & =-3
\end{aligned}

x=x= \qquad y=y= \qquad z=z= \qquad
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Answer from Sia
Posted 9 months ago
Solution by Steps
step 1
Write the augmented matrix for the given system of equations: (435431815163) \begin{pmatrix} 4 & -3 & -5 & | & -4 \\ 3 & 1 & -8 & | & -1 \\ -5 & 1 & 6 & | & -3 \end{pmatrix}
step 2
Perform row operations to get a leading 1 in the first row, first column. Divide the first row by 4: (13454131815163) \begin{pmatrix} 1 & -\frac{3}{4} & -\frac{5}{4} & | & -1 \\ 3 & 1 & -8 & | & -1 \\ -5 & 1 & 6 & | & -3 \end{pmatrix}
step 3
Eliminate the first column entries below the leading 1 by performing row operations: R2=R23R1andR3=R3+5R1 R2 = R2 - 3R1 \quad \text{and} \quad R3 = R3 + 5R1 (1345410134174201141148) \begin{pmatrix} 1 & -\frac{3}{4} & -\frac{5}{4} & | & -1 \\ 0 & \frac{13}{4} & -\frac{17}{4} & | & 2 \\ 0 & -\frac{11}{4} & \frac{11}{4} & | & -8 \end{pmatrix}
step 4
Normalize the second row by dividing by 134\frac{13}{4}: R2=413R2 R2 = \frac{4}{13} R2 (13454101171381301141148) \begin{pmatrix} 1 & -\frac{3}{4} & -\frac{5}{4} & | & -1 \\ 0 & 1 & -\frac{17}{13} & | & \frac{8}{13} \\ 0 & -\frac{11}{4} & \frac{11}{4} & | & -8 \end{pmatrix}
step 5
Eliminate the second column entries below and above the leading 1 in the second row: R3=R3+114R2andR1=R1+34R2 R3 = R3 + \frac{11}{4} R2 \quad \text{and} \quad R1 = R1 + \frac{3}{4} R2 (1029135130117138130001013) \begin{pmatrix} 1 & 0 & -\frac{29}{13} & | & -\frac{5}{13} \\ 0 & 1 & -\frac{17}{13} & | & \frac{8}{13} \\ 0 & 0 & 0 & | & -\frac{10}{13} \end{pmatrix}
step 6
Since the third row results in 0=10130 = -\frac{10}{13}, which is a contradiction, the system has no solutions
Answer
x=Nx = N, y=Ny = N, z=Nz = N
Key Concept
Gaussian Elimination
Explanation
Gaussian elimination is used to solve systems of linear equations by transforming the system's augmented matrix into row-echelon form. If a row results in a contradiction, the system has no solutions.

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