Math Problem Statement

find area y=-x^2+6,y=mod x

Solution

We need to find the area enclosed by the curves:

  1. y=x2+6y = -x^2 + 6 (a downward-facing parabola)
  2. y=xy = |x| (a V-shaped absolute value function)

Step 1: Find Intersection Points

To determine the limits of integration, we solve:

x2+6=x-x^2 + 6 = |x|

For x0x \geq 0 (i.e., y=xy = x)

x2+6=x-x^2 + 6 = x x2x+6=0-x^2 - x + 6 = 0 Solving this quadratic equation:

x2+x6=0x^2 + x - 6 = 0

Factoring:

(x+3)(x2)=0(x + 3)(x - 2) = 0

So, x=3x = -3 or x=2x = 2. Since we're in x0x \geq 0, we take x=2x = 2.

For x0x \leq 0 (i.e., y=xy = -x)

x2+6=x-x^2 + 6 = -x x2+x+6=0-x^2 + x + 6 = 0

Rewriting:

x2x6=0x^2 - x - 6 = 0

Factoring:

(x3)(x+2)=0(x - 3)(x + 2) = 0

So, x=3x = 3 or x=2x = -2. Since we're in x0x \leq 0, we take x=2x = -2.

Thus, the curves intersect at x=2x = -2 and x=2x = 2.

Step 2: Set Up the Integral

The area is symmetric about the y-axis, so we compute for x[0,2]x \in [0,2] and double the result.

A=202[(x2+6)x]dxA = 2 \int_0^2 [(-x^2 + 6) - x] \,dx

Simplifying:

A=202(x2+6x)dxA = 2 \int_0^2 (-x^2 + 6 - x) \,dx

A=202(x2x+6)dxA = 2 \int_0^2 (-x^2 - x + 6) \,dx

Step 3: Compute the Integral

Breaking it down:

(x2x+6)dx=x2dx+xdx+6dx\int (-x^2 - x + 6) \,dx = \int -x^2 \,dx + \int -x \,dx + \int 6 \,dx

[ = \left[ -\frac{x^3}{3} \right] + \left[ -\frac{x^2}{2} \right] + \left[ 6x \right] \Big|_0^2 ]

Evaluating at x=2x = 2:

(8342+6(2))=(832+12)=(86+363)=223\left( -\frac{8}{3} - \frac{4}{2} + 6(2) \right) = \left( -\frac{8}{3} - 2 + 12 \right) = \left( \frac{-8 - 6 + 36}{3} \right) = \frac{22}{3}

Evaluating at x=0x = 0:

00

So,

A=2×223=443A = 2 \times \frac{22}{3} = \frac{44}{3}

Final Answer:

443 square units\frac{44}{3} \text{ square units}

Would you like a graphical representation or further details?

Related Questions:

  1. How do you find the enclosed area between two curves using definite integrals?
  2. How does symmetry simplify area calculations in integrals?
  3. What are the key steps in solving quadratic equations for intersection points?
  4. How do modulus functions affect integration limits?
  5. What is the geometric interpretation of this integral?

Tip:

When integrating to find the area, always check which function is on top and subtract accordingly to avoid negative areas.

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Math Problem Analysis

Mathematical Concepts

Calculus
Definite Integrals
Area Between Curves
Quadratic Functions
Absolute Value Functions

Formulas

Definite integral
Area between curves: A = ∫[a,b] (f(x) - g(x)) dx

Theorems

The Fundamental Theorem of Calculus
Symmetry in integrals

Suitable Grade Level

Grades 11-12