Math Problem Statement

The diagram below shows the graph of y = x^2 - 3x - 1. What line should you add to the graph in order to solve the equation x^2 - 7x + 4 = 0? Give your answer in the form y = mx + c.

Solution

To solve the problem, we are looking for a line in the form y=mx+cy = mx + c that allows the quadratic equation x27x+4=0x^2 - 7x + 4 = 0 to be solved using the intersection points between this line and the given parabola y=x23x1y = x^2 - 3x - 1.

Steps:

  1. Rewrite x27x+4=0x^2 - 7x + 4 = 0 as a system: The equation x27x+4=0x^2 - 7x + 4 = 0 represents a parabola equal to some other line yy.

    Start by rearranging the quadratic equation: x27x+4=yx^2 - 7x + 4 = y To solve for intersection points, compare this to the given equation: x23x1=yx^2 - 3x - 1 = y

  2. Set up equality: Since x23x1=x27x+4x^2 - 3x - 1 = x^2 - 7x + 4, cancel out x2x^2 (it appears in both): 3x1=7x+4-3x - 1 = -7x + 4

  3. Solve for xx: Rearrange terms: 4x=54x = 5 x=54x = \frac{5}{4}

  4. Find corresponding yy: Substitute x=54x = \frac{5}{4} into one of the equations for yy. Using y=x27x+4y = x^2 - 7x + 4: y=(54)27(54)+4y = \left(\frac{5}{4}\right)^2 - 7\left(\frac{5}{4}\right) + 4 Simplify: y=2516354+4= ⁣!Tocorrectlyapproachthis,insteadofsolvingintersectionpointsdirectly,wedeterminetherequiredlinethatrepresentstheequationy = \frac{25}{16} - \frac{35}{4} + 4 = \dots\!! To correctly approach this, instead of solving intersection points directly, we determine the required **line** that represents the equation x^2 - 7x + 4 = 0$$ as another function:

Step-by-Step Solution:

  1. Rewriting x27x+4=0x^2 - 7x + 4 = 0 as a system: The new parabola can be represented as: [ y = x^2 - 7x + 4$$

  2. Find the line to add to the graph: Since we are finding where this new parabola intersects the existing one, y=x23x1y = x^2 - 3x - 1, we subtract the equations: (x27x+4)(x23x1)=0(x^2 - 7x + 4) - (x^2 - 3x - 1) = 0

    Simplify: 7x+4+3x+1=0-7x + 4 + 3x + 1 = 0

    Combine like terms: 4x+5=0-4x + 5 = 0

    Solve for yy: y=4x5y = 4x - 5

Final Answer:

The line that should be added to the graph is: y=4x5y = 4x - 5


Would you like further clarification or a visual explanation? Here are related questions you might consider:

  1. What does the graph of y=4x5y = 4x - 5 look like relative to the parabola?
  2. How do we interpret the intersection points between the parabola and this line?
  3. Could we have solved this using graphing instead of algebraic manipulation?
  4. How does changing the constant cc in y=mx+cy = mx + c affect the solution?
  5. How would this method change if the quadratic had a leading coefficient other than 1?

Tip: Always align your equations carefully when setting up intersections—they represent simultaneous solutions!

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Linear Equations
Intersection of Functions

Formulas

y = mx + c
Quadratic equation: ax^2 + bx + c = 0

Theorems

Intersection of two functions
Equality of polynomials

Suitable Grade Level

Grades 8-10