Math Problem Statement

Find the coordinates of the points of intersection of the graphs of y = 2x^2 + x - 1 and 2y - 3x = 58.

Solution

To find the points of intersection of the two given equations:

  1. y=2x2+x1y = 2x^2 + x - 1
  2. 2y3x=582y - 3x = 58

we solve them simultaneously.

Step 1: Rearrange the second equation

Rearranging 2y3x=582y - 3x = 58 for yy: 2y=3x+582y = 3x + 58 y=3x2+29y = \frac{3x}{2} + 29

Step 2: Substitute yy into the first equation

Substitute y=3x2+29y = \frac{3x}{2} + 29 into y=2x2+x1y = 2x^2 + x - 1: 3x2+29=2x2+x1\frac{3x}{2} + 29 = 2x^2 + x - 1

Multiply through by 2 to eliminate the fraction: 3x+58=4x2+2x23x + 58 = 4x^2 + 2x - 2

Simplify: 4x2x60=04x^2 - x - 60 = 0

Step 3: Solve the quadratic equation

The quadratic equation is 4x2x60=04x^2 - x - 60 = 0. Using the quadratic formula: x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} where a=4a = 4, b=1b = -1, c=60c = -60.

x=(1)±(1)24(4)(60)2(4)x = \frac{-(-1) \pm \sqrt{(-1)^2 - 4(4)(-60)}}{2(4)} x=1±1+9608x = \frac{1 \pm \sqrt{1 + 960}}{8} x=1±9618x = \frac{1 \pm \sqrt{961}}{8} x=1±318x = \frac{1 \pm 31}{8}

So: x=328=4orx=308=154.x = \frac{32}{8} = 4 \quad \text{or} \quad x = \frac{-30}{8} = -\frac{15}{4}.

Step 4: Find corresponding yy-values

For x=4x = 4, substitute into y=3x2+29y = \frac{3x}{2} + 29: y=3(4)2+29=6+29=35.y = \frac{3(4)}{2} + 29 = 6 + 29 = 35.

For x=154x = -\frac{15}{4}, substitute into y=3x2+29y = \frac{3x}{2} + 29: y=3(154)2+29=458+29=45+2328=1878.y = \frac{3(-\frac{15}{4})}{2} + 29 = -\frac{45}{8} + 29 = \frac{-45 + 232}{8} = \frac{187}{8}.

Final Answer:

The points of intersection are: (4,35)and(154,1878).(4, 35) \quad \text{and} \quad \left(-\frac{15}{4}, \frac{187}{8}\right).

Would you like detailed steps for the quadratic formula or simplification?

Here are some related questions to explore:

  1. How do we confirm these points are correct graphically?
  2. What methods other than substitution can solve simultaneous equations?
  3. How does the shape of the parabola affect the number of intersection points?
  4. Can this problem be solved numerically or by approximation?
  5. What role does the quadratic discriminant play in determining the solutions?

Tip: Always check your solutions by substituting them back into both original equations.

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Math Problem Analysis

Mathematical Concepts

Simultaneous Equations
Quadratic Functions
Algebra

Formulas

y = mx + c (linear equation form)
Quadratic equation formula: ax^2 + bx + c = 0
Quadratic formula: x = [-b ± √(b² - 4ac)] / 2a

Theorems

Quadratic Formula
Substitution Method for Solving Simultaneous Equations

Suitable Grade Level

Grades 9-12