A system of three equations and their graphs in the xy-plane are shown.

[tex]\[
\begin{array}{l}
y = \frac{1}{4}x + 2 \\
y = -x^2 + 4x + 3 \\
x^2 + y^2 = 25
\end{array}
\][/tex]

How many solutions does the system have?

A. One
B. Two
C. Three
D. Four



Answer :

To solve the system of equations and find the number of solutions, let's analyze each pair of equations step-by-step and then combine the solutions.

Given system of equations:

1. [tex]\( y = \frac{1}{4}x + 2 \)[/tex]
2. [tex]\( y = -x^2 + 4x + 3 \)[/tex]
3. [tex]\( x^2 + y^2 = 25 \)[/tex]

Step-by-Step Solution:

### Step 1: Solve Equation 1 and Equation 2 Together

Equation 1: [tex]\( y = \frac{1}{4}x + 2 \)[/tex]

Equation 2: [tex]\( y = -x^2 + 4x + 3 \)[/tex]

Set these equations equal to each other:
[tex]\[ \frac{1}{4}x + 2 = -x^2 + 4x + 3 \][/tex]

Multiply through by 4 to clear the fraction:
[tex]\[ x + 8 = -4x^2 + 16x + 12 \][/tex]

Rearrange to form a standard quadratic equation:
[tex]\[ 4x^2 - 15x + 4 = 0 \][/tex]

Solve this quadratic equation using the quadratic formula [tex]\( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \)[/tex]:
[tex]\[ x_1 = 4, \quad x_2 = -0.25 \][/tex]

Substitute these [tex]\( x \)[/tex] values back into either Equation 1 or Equation 2 to find corresponding [tex]\( y \)[/tex] values:
For [tex]\( x = 4 \)[/tex]:
[tex]\[ y = \frac{1}{4}(4) + 2 = 3 \][/tex]

For [tex]\( x = -0.25 \)[/tex]:
[tex]\[ y = \frac{1}{4}(-0.25) + 2 \approx 1.9375 \][/tex]

Solutions for Equations 1 and 2:
[tex]\[ (4, 3), \quad (-0.25, 1.9375) \][/tex]

### Step 2: Solve Equation 1 and Equation 3 Together

Equation 1: [tex]\( y = \frac{1}{4}x + 2 \)[/tex]

Equation 3: [tex]\( x^2 + y^2 = 25 \)[/tex]

Substitute Equation 1 into Equation 3:
[tex]\[ x^2 + \left(\frac{1}{4}x + 2\right)^2 = 25 \][/tex]

Expand and simplify:
[tex]\[ x^2 + \frac{1}{16}x^2 + x + 4 = 25 \][/tex]

This results in a cubic equation with roots:
[tex]\[ x \approx -4.941 \][/tex] (complex solutions are omitted for simplicity)

Substitute these [tex]\( x \)[/tex] values back into Equation 1:
For [tex]\( x = -4.941 \)[/tex]:
[tex]\[ y = \frac{1}{4}(-4.941) + 2 \approx 0.765 \][/tex]

Solutions for Equations 1 and 3:
[tex]\[ (-4.941, 0.765) \][/tex]

### Step 3: Solve Equation 2 and Equation 3 Together

Equation 2: [tex]\( y = -x^2 + 4x + 3 \)[/tex]

Equation 3: [tex]\( x^2 + y^2 = 25 \)[/tex]

This results in higher-order polynomial equations with roots:
[tex]\[ x = 4 \][/tex]

Substitute these [tex]\( x \)[/tex] values back into Equation 2:
For [tex]\( x = 4 \)[/tex]:
[tex]\[ y = -4^2 + 4(4) + 3 = 3 \][/tex]

The solutions may also include some complex roots.

Solutions for Equations 2 and 3:
[tex]\[ (4, 3) \][/tex]

### Conclusion

After solving each pair of equations, we combine all unique solutions:

[tex]\[ (4, 3), \quad (-0.25, 1.9375), \quad (-4.941, 0.765) \][/tex]

Here are known significant unique solutions:
1. [tex]\( (4, 3) \)[/tex]
2. [tex]\( (-0.25, 1.9375) \)[/tex]
3. [tex]\( (-4.941, 0.765) \)[/tex]

Given the total number of unique solutions is seven, we consider all possible real and complex roots combined. Thus, the complete solution for the number of solutions in the system is:

Answer: Seven