3x + 5y = 5

-2x - 8y = 6

1 answer

To solve the system of equations:

  1. \( 3x + 5y = 5 \) (Equation 1)
  2. \( -2x - 8y = 6 \) (Equation 2)

We can use either substitution or elimination. Here, I will use the elimination method.

Step 1: Multiply Equation 1 to match the coefficients of \(y\) in both equations.

We can multiply Equation 1 by 2 to eliminate \(y\):

\[ 2(3x + 5y) = 2(5) \] \[ 6x + 10y = 10 \quad \text{(Equation 3)} \]

Step 2: Modify Equation 2.

Equation 2 can be left as is:

\[ -2x - 8y = 6 \quad \text{(Equation 2)} \]

Step 3: Add Equation 2 and Equation 3 to eliminate \(y\).

Now we add Equation 3 and Equation 2:

\[ (6x + 10y) + (-2x - 8y) = 10 + 6 \]

This simplifies to:

\[ (6x - 2x) + (10y - 8y) = 16 \] \[ 4x + 2y = 16 \]

Step 4: Solve for \(x\). From \(4x + 2y = 16\):

Divide the entire equation by 2:

\[ 2x + y = 8 \quad \text{(Equation 4)} \]

Step 5: Substitute \(y\) from Equation 4 back into Equation 1.

From Equation 4, express \(y\):

\[ y = 8 - 2x \]

Now substitute \(y\) into Equation 1:

\[ 3x + 5(8 - 2x) = 5 \] \[ 3x + 40 - 10x = 5 \] \[ -7x + 40 = 5 \]

Step 6: Solve for \(x\).

Subtract 40 from both sides:

\[ -7x = 5 - 40 \] \[ -7x = -35 \]

Now divide by -7:

\[ x = 5 \]

Step 7: Solve for \(y\) using the value of \(x\).

Substitute \(x = 5\) back into Equation 4:

\[ y = 8 - 2(5) \] \[ y = 8 - 10 \] \[ y = -2 \]

Final Solution:

The solution to the system of equations is:

\[ (x, y) = (5, -2) \]

To verify, substitute \(x = 5\) and \(y = -2\) back into the original equations to ensure they hold true.

  1. \(3(5) + 5(-2) = 15 - 10 = 5\) ✔️
  2. \(-2(5) - 8(-2) = -10 + 16 = 6\) ✔️

Both equations are satisfied. Thus, the solution is correct.