Solve the System of Equations: -8x + 3y = 7 and 24x + y = 3

Question

Solve the above set of equations and choose the correct answer.

{8x+3y=724x+y=3 \begin{cases} -8x+3y=7 \\ 24x+y=3 \end{cases}

Video Solution

Step-by-Step Solution

We will solve the system of equations using the elimination method.

Step 1: We have the system of equations:

  • Equation 1: 8x+3y=7-8x + 3y = 7
  • Equation 2: 24x+y=324x + y = 3

Step 2: Let's eliminate xx by aligning coefficients. Multiply Equation 1 by 3:

Equation 1: 8x+3y=7-8x + 3y = 7 becomes 24x+9y=21-24x + 9y = 21

Now subtract Equation 2 from the modified Equation 1:

24x+9y(24x+y)=213-24x + 9y - (24x + y) = 21 - 3

Simplifying, we get:

48x+8y=18-48x + 8y = 18

Notice, this was incorrect since subtraction led to an error in understanding coefficients. Let's find yy directly.

We have:

  • Equation 1: 8x+3y=7-8x + 3y = 7
  • Equation 2: 24x+y=324x + y = 3

Step 3: Solve for yy from Equation 2:

Multiply Equation 2 by 3:

24x+y=324x + y = 3

3 (24x+y=3)(24x + y = 3) gives:

72x+3y=972x + 3y = 9

Subtracting Equation 1 from this new Equation gives:

(72x+3y)(8x+3y)=97(72x + 3y) - (-8x + 3y) = 9 - 7

80x=280x = 2

Step 4: Solve for xx:

x=280=0.025x = \frac{2}{80} = 0.025

Step 5: Substitute x=0.025x = 0.025 back into Equation 2 to find yy:

24(0.025)+y=324(0.025) + y = 3

0.6+y=30.6 + y = 3

y=30.6=2.4y = 3 - 0.6 = 2.4

Thus, the solution to the system of equations is x=0.025x = 0.025 and y=2.4y = 2.4.

The choice corresponding to this solution is:

x=0.025,y=2.4x = 0.025, y = 2.4

Answer

x=0.025,y=2.4 x=0.025,y=2.4