Math Problem Statement

Find the area enclosed by the x-axis and the straight lines x= 3y - 5 and 2y= 7 + 3x

Solution

To find the area enclosed by the x-axis and the straight lines x=3y5x = 3y - 5 and 2y=7+3x2y = 7 + 3x, we need to follow a systematic approach.

Step 1: Write equations of the lines in terms of yy

Given the two equations:

  1. x=3y5x = 3y - 5
  2. 2y=7+3x2y = 7 + 3x

Let's rewrite them both in the standard form y=f(x)y = f(x).

Equation 1: x=3y5x = 3y - 5

Solve for yy: y=x+53y = \frac{x + 5}{3}

Equation 2: 2y=7+3x2y = 7 + 3x

Solve for yy: y=7+3x2y = \frac{7 + 3x}{2}

Now, the two lines are: y=x+53(Line 1)y = \frac{x + 5}{3} \quad \text{(Line 1)} y=7+3x2(Line 2)y = \frac{7 + 3x}{2} \quad \text{(Line 2)}

Step 2: Find points of intersection

To find the points of intersection with each other and with the x-axis, we first set the two equations equal to each other to find their intersection:

x+53=7+3x2\frac{x + 5}{3} = \frac{7 + 3x}{2}

Multiply through by 6 (the least common denominator):

2(x+5)=3(7+3x)2(x + 5) = 3(7 + 3x)

Expand both sides:

2x+10=21+9x2x + 10 = 21 + 9x

Simplify:

1021=9x2x10 - 21 = 9x - 2x 11=7x-11 = 7x x=117x = -\frac{11}{7}

Now substitute x=117x = -\frac{11}{7} into either equation to find yy. Using the first equation:

y=x+53=117+53y = \frac{x + 5}{3} = \frac{-\frac{11}{7} + 5}{3} First, convert 5 to a fraction with denominator 7:

5=3575 = \frac{35}{7} Now:

y=117+3573=2473=2421=87y = \frac{-\frac{11}{7} + \frac{35}{7}}{3} = \frac{\frac{24}{7}}{3} = \frac{24}{21} = \frac{8}{7}

So, the lines intersect at (117,87)\left(-\frac{11}{7}, \frac{8}{7}\right).

Step 3: Find intercepts with the x-axis

The intercepts with the x-axis occur where y=0y = 0.

For Line 1: y=x+53y = \frac{x + 5}{3}

Set y=0y = 0:

0=x+530 = \frac{x + 5}{3} x=5x = -5

So, Line 1 intersects the x-axis at x=5x = -5.

For Line 2: y=7+3x2y = \frac{7 + 3x}{2}

Set y=0y = 0:

0=7+3x20 = \frac{7 + 3x}{2} 7+3x=07 + 3x = 0 x=73x = -\frac{7}{3}

So, Line 2 intersects the x-axis at x=73x = -\frac{7}{3}.

Step 4: Set up the integral to find the area

The area enclosed by the x-axis and the lines can be found by integrating the difference between the two functions from the leftmost x-intercept to the rightmost x-intercept.

The limits of integration are from x=5x = -5 to x=73x = -\frac{7}{3}, and the functions are:

y1=x+53,y2=7+3x2y_1 = \frac{x + 5}{3}, \quad y_2 = \frac{7 + 3x}{2}

The enclosed area is given by:

Area=573(7+3x2x+53)dx\text{Area} = \int_{-5}^{-\frac{7}{3}} \left( \frac{7 + 3x}{2} - \frac{x + 5}{3} \right) dx

Step 5: Compute the integral

First, simplify the integrand:

[ \frac{7 + 3x}{2} - \frac{x + 5}{3} = \frac{3(7 + 3x) - 2(x +

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Math Problem Analysis

Mathematical Concepts

Coordinate Geometry
Integration
Linear Equations

Formulas

y = (x + 5) / 3
y = (7 + 3x) / 2
Area = ∫[a to b] (f(x) - g(x)) dx

Theorems

Intersection of Lines
Definite Integration

Suitable Grade Level

Grades 10-12