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Solve the system of linear equations. \[ \left\{\begin{array}{rr}x+2 y-7 z= & -4 \\ 2 x+3 y+z= & 5 \\ 3 x+7 y-36 z= & -25\end{array}\right. \]

Ask by Bowman Graham. in the United States
Jan 22,2025

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Tutor-Verified Answer

Answer

The system of equations has infinitely many solutions.

Solution

Solve the system of equations \( x+2y-7z=-4;2x+3y+z=5;3x+7y-36z=-25 \). Solve the system of equations by following steps: - step0: Solve using the substitution method: \(\left\{ \begin{array}{l}x+2y-7z=-4\\2x+3y+z=5\\3x+7y-36z=-25\end{array}\right.\) - step1: Solve the equation: \(\left\{ \begin{array}{l}x=-4-2y+7z\\2x+3y+z=5\\3x+7y-36z=-25\end{array}\right.\) - step2: Substitute the value of \(x:\) \(\left\{ \begin{array}{l}2\left(-4-2y+7z\right)+3y+z=5\\3\left(-4-2y+7z\right)+7y-36z=-25\end{array}\right.\) - step3: Simplify: \(\left\{ \begin{array}{l}-8-y+15z=5\\-12+y-15z=-25\end{array}\right.\) - step4: Solve the equation: \(\left\{ \begin{array}{l}y=-13+15z\\-12+y-15z=-25\end{array}\right.\) - step5: Substitute the value of \(y:\) \(-12-13+15z-15z=-25\) - step6: Simplify: \(-25=-25\) - step7: Substitute the value of \(y:\) \(x=-4-2\left(-13+15z\right)+7z\) - step8: Simplify: \(x=22-23z\) - step9: Calculate: \(\left(x,y,z\right) = \left(22-23z,-13+15z,z\right),z \in \mathbb{R}\) - step10: Alternative Form: \(\textrm{Infinitely many solutions}\) The system of linear equations has infinitely many solutions.

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Bonus Knowledge

To solve the given system of linear equations, we can use the method of substitution or elimination. Here's how to approach it step by step: We have the system: 1. \( x + 2y - 7z = -4 \) (Equation 1) 2. \( 2x + 3y + z = 5 \) (Equation 2) 3. \( 3x + 7y - 36z = -25 \) (Equation 3) Let's solve this system. First, let's express \( x \) from Equation 1: \[ x = -4 - 2y + 7z \quad (4) \] Now substitute Equation (4) into Equations 2 and 3: Substituting into Equation 2: \[ 2(-4 - 2y + 7z) + 3y + z = 5 \] \[ -8 - 4y + 14z + 3y + z = 5 \] \[ -8 - y + 15z = 5 \] \[ -y + 15z = 13 \quad (5) \] Now substitute Equation (4) into Equation 3: \[ 3(-4 - 2y + 7z) + 7y - 36z = -25 \] \[ -12 - 6y + 21z + 7y - 36z = -25 \] \[ -12 + y - 15z = -25 \] \[ y - 15z = -13 \quad (6) \] Now we have the new system of equations (5) and (6): 1. \(-y + 15z = 13\) (Equation 5) 2. \(y - 15z = -13\) (Equation 6) Adding Equations (5) and (6): \[ (-y + 15z) + (y - 15z) = 13 - 13 \] \[ 0 = 0 \] This shows that the two equations are dependent, confirming they represent the same line. Therefore, we can solve for \( y \) in terms of \( z \). From Equation (5): \[ y = 15z + 13 \quad (7) \] Now substituting Equation (7) back into Equation (4): \[ x = -4 - 2(15z + 13) + 7z \] \[ x = -4 - 30z - 26 + 7z \] \[ x = -30 - 23z \] Now we can express the solution as parametric equations in terms of \( z \): \[ x = -30 - 23z, \quad y = 15z + 13, \quad z = z \] Thus, the general solution is: \[ \boxed{(x, y, z) = (-30 - 23t, 15t + 13, t) \text{ for any } t \in \mathbb{R}} \]

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