find the area of the following shape. you must show all work to receive credit.

find the area of the following shape. you must show all work to receive credit.

find the area of the following shape. you must show all work to receive credit.

Answer

Explanation:

Step1: Decompose the shape

The shape can be divided into a rectangle and a triangle. The rectangle has length from ( x = -1 ) to ( x = -4 ) (length ( 3 )) and height from ( y = 0 ) to ( y = 2 ) (height ( 2 ))? Wait, no, let's check coordinates. Wait, the rectangle is from ( x=-1 ) to ( x=-4 )? No, wait the bottom horizontal line is from ( x=-4 ) to ( x=-1 ) (length ( 3 )), vertical from ( x=-1 ) up to ( y=2 ) (height ( 2 )), so rectangle area: ( length \times height = 3 \times 2 = 6 )? Wait no, wait the vertical side: from ( y=0 ) to ( y=2 ), so height is ( 2 ), length is ( 3 ) (from ( x=-4 ) to ( x=-1 ), that's ( 3 ) units). Then the triangle: the top part. The base of the triangle: from ( x=-1 ) to ( x=2 )? Wait no, the triangle has vertices at ( (0,4) ), ( (2,2) ), and ( (-1,2) )? Wait no, let's list the vertices. The blue shape: let's find all vertices. From the graph: the points are ( (-4,0) ), ( (-1,0) ), ( (-1,2) ), ( (2,2) ), ( (0,4) ), back to ( (-4,0) )? Wait, no, connecting ( (-4,0) ) to ( (-1,0) ) (horizontal), ( (-1,0) ) to ( (-1,2) ) (vertical), ( (-1,2) ) to ( (2,2) ) (horizontal), ( (2,2) ) to ( (0,4) ) (line), ( (0,4) ) to ( (-4,0) ) (line). So we can split into a rectangle and a triangle. The rectangle is ( (-4,0) ), ( (-1,0) ), ( (-1,2) ), ( (x_1,2) )? Wait, no, the rectangle is from ( x=-4 ) to ( x=-1 ), ( y=0 ) to ( y=2 ): that's a rectangle with length ( 3 ) (from -4 to -1 is 3 units) and height ( 2 ) (from 0 to 2), area ( 3 \times 2 = 6 ). Then the triangle: the top part, with vertices ( (-1,2) ), ( (2,2) ), ( (0,4) ). The base of the triangle is the distance between ( (-1,2) ) and ( (2,2) ), which is ( 3 ) units (from -1 to 2 is 3 units), and the height is the vertical distance from ( (0,4) ) to ( y=2 ), which is ( 2 ) units. So triangle area: ( \frac{1}{2} \times base \times height = \frac{1}{2} \times 3 \times 2 = 3 ). Wait, but wait, is the triangle's base correct? Wait, the three points of the triangle: ( (-1,2) ), ( (2,2) ), ( (0,4) ). The base is between ( (-1,2) ) and ( (2,2) ), length ( 3 ), height is ( 4 - 2 = 2 ), so area ( \frac{1}{2} \times 3 \times 2 = 3 ). Then total area: rectangle area + triangle area = ( 6 + 3 = 9 )? Wait, no, wait another way: use the shoelace formula. Let's list the coordinates in order: ( (-4,0) ), ( (-1,0) ), ( (-1,2) ), ( (2,2) ), ( (0,4) ), back to ( (-4,0) ). Shoelace formula: ( \frac{1}{2} |\sum_{i=1}^{n} (x_i y_{i+1} - x_{i+1} y_i)| ).

Calculating:

( x_1=-4, y_1=0 )

( x_2=-1, y_2=0 )

( x_3=-1, y_3=2 )

( x_4=2, y_4=2 )

( x_5=0, y_5=4 )

( x_6=-4, y_6=0 )

Compute sum of ( x_i y_{i+1} ):

( (-4)(0) + (-1)(2) + (-1)(2) + (2)(4) + (0)(0) = 0 - 2 - 2 + 8 + 0 = 4 )

Compute sum of ( y_i x_{i+1} ):

( (0)(-1) + (0)(-1) + (2)(2) + (2)(0) + (4)(-4) = 0 + 0 + 4 + 0 - 16 = -12 )

Subtract: ( 4 - (-12) = 16 ), take absolute value and multiply by ( \frac{1}{2} ): ( \frac{1}{2} \times 16 = 8 )? Wait, that's different. Wait, maybe I listed the coordinates wrong. Let's recheck the vertices. Let's trace the shape:

Start at ( (-4, 0) ), go to ( (-1, 0) ) (right along x-axis), then up to ( (-1, 2) ) (vertical), then right to ( (2, 2) ) (horizontal), then up to ( (0, 4) ) (line), then left down to ( (-4, 0) ) (line). So the vertices are ( A(-4,0) ), ( B(-1,0) ), ( C(-1,2) ), ( D(2,2) ), ( E(0,4) ), back to ( A(-4,0) ).

Now apply shoelace formula:

List the coordinates in order:

( A(-4,0) ), ( B(-1,0) ), ( C(-1,2) ), ( D(2,2) ), ( E(0,4) ), ( A(-4,0) )

Compute ( \sum x_i y_{i+1} ):

( (-4)(0) + (-1)(2) + (-1)(2) + (2)(4) + (0)(0) = 0 - 2 - 2 + 8 + 0 = 4 )

Compute ( \sum y_i x_{i+1} ):

( (0)(-1) + (0)(-1) + (2)(2) + (2)(0) + (4)(-4) = 0 + 0 + 4 + 0 - 16 = -12 )

Now, ( |\sum x_i y_{i+1} - \sum y_i x_{i+1}| = |4 - (-12)| = 16 ), then area is ( \frac{1}{2} \times 16 = 8 ). Wait, but maybe splitting into rectangle and triangle is better. Let's split into rectangle ( A(-4,0) ), ( B(-1,0) ), ( C(-1,2) ), ( F(-4,2) ) (a rectangle with length 3, height 2, area 6) and then the polygon ( F(-4,2) ), ( C(-1,2) ), ( D(2,2) ), ( E(0,4) ), ( A(-4,0) )? No, that's not right. Wait, maybe the top part is a triangle and a trapezoid? Wait, no, let's use another method. The shape can be seen as a rectangle plus a triangle. Wait, the rectangle is from ( x=-4 ) to ( x=-1 ), ( y=0 ) to ( y=2 ): area ( 3 \times 2 = 6 ). Then the upper part: from ( x=-1 ) to ( x=2 ), ( y=2 ) to ( y=4 ). Wait, the upper part is a triangle? Wait, the points ( (-1,2) ), ( (2,2) ), ( (0,4) ). So that's a triangle with base ( 3 ) (from -1 to 2 is 3 units) and height ( 2 ) (from 2 to 4 is 2 units). Area of triangle: ( \frac{1}{2} \times 3 \times 2 = 3 ). Then total area: ( 6 + 3 = 9 ). But shoelace gave 8. There's a mistake. Wait, let's check the coordinates again. Wait, the point ( (0,4) ) to ( (-4,0) ): let's see the slope. From ( (0,4) ) to ( (-4,0) ), slope is ( (0-4)/(-4-0) = (-4)/(-4) = 1 ), so equation ( y = x + 4 ). At ( x=-1 ), ( y = -1 + 4 = 3 ), but the point at ( x=-1 ) is ( (-1,2) ). Wait, so my vertex list was wrong. Oh! I see the mistake. The vertical line is from ( (-1,0) ) to ( (-1,2) ), then horizontal to ( (2,2) ), then the line from ( (2,2) ) to ( (0,4) ), then the line from ( (0,4) ) to ( (-4,0) ), and the line from ( (-4,0) ) to ( (-1,0) ). So the correct vertices are: ( (-4,0) ), ( (-1,0) ), ( (-1,2) ), ( (2,2) ), ( (0,4) ), and back to ( (-4,0) ). Wait, but at ( x=-1 ), the y-coordinate is 2, and the line from ( (0,4) ) to ( (-4,0) ) passes through ( x=-1 ), ( y=3 ), but the shape has a vertical line at ( x=-1 ) up to ( y=2 ), so the shape is a rectangle (from ( -4,0 ) to ( -1,0 ) to ( -1,2 ) to ( x_1,2 ) to ( -4,0 ))? No, the horizontal line from ( -1,2 ) to ( 2,2 ) is correct, then from ( 2,2 ) to ( 0,4 ), then from ( 0,4 ) to ( -4,0 ), and from ( -4,0 ) to ( -1,0 ), and from ( -1,0 ) to ( -1,2 ). So the area can be calculated as the area of the rectangle (from ( -4,0 ) to ( -1,0 ) to ( -1,2 ) to ( -4,2 ) to ( -4,0 )) plus the area of the trapezoid or triangle above the rectangle. Wait, the rectangle is ( 3 ) (length) by ( 2 ) (height), area ( 6 ). Then the area above the rectangle: the region from ( y=2 ) to ( y=4 ), from ( x=-4 ) to ( x=2 ), but bounded by the line ( y = x + 4 ) (from ( (0,4) ) to ( (-4,0) )) and the line from ( (2,2) ) to ( (0,4) ) (slope ( (4-2)/(0-2) = 2/(-2) = -1 ), equation ( y = -x + 4 )). Wait, at ( x=2 ), ( y = -2 + 4 = 2 ), correct. At ( x=-1 ), ( y = 1 + 4 = 3 ) (from ( y = x + 4 )) and ( y = 1 + 4 = 3 ) (from ( y = -x + 4 ) at ( x=-1 ) is ( y = 1 + 4 = 5 )? No, wait ( y = -x + 4 ) at ( x=-1 ) is ( y = 1 + 4 = 5 ), which is not correct. I'm getting confused. Let's use the grid method. Each square is 1x1. Let's count the squares or use the formula for composite shapes.

Alternative approach: Divide the shape into two parts: a rectangle and a triangle.

  1. Rectangle: from ( x = -4 ) to ( x = -1 ) (length 3), ( y = 0 ) to ( y = 2 ) (height 2). Area: ( 3 \times 2 = 6 ).

  2. Triangle: The top part. The base of the triangle is from ( x = -1 ) to ( x = 2 ) (length 3), and the height is from ( y = 2 ) to ( y = 4 ) (height 2). Wait, no, the triangle has vertices at ( (-1,2) ), ( (2,2) ), and ( (0,4) ). The base is 3 (from -1 to 2), height is 2 (from 2 to 4), so area ( \frac{1}{2} \times 3 \times 2 = 3 ). But wait, the line from ( (0,4) ) to ( (-4,0) ) passes through ( x=-1 ), ( y=3 ), but the shape has a vertical line at ( x=-1 ) up to ( y=2 ), so there's a small rectangle or a mistake? Wait, no, the correct way is to use the shoelace formula with correct coordinates. Let's list the correct vertices:

  • ( (-4, 0) )
  • ( (-1, 0) )
  • ( (-1, 2) )
  • ( (2, 2) )
  • ( (0, 4) )
  • ( (-4, 0) )

Now apply shoelace formula:

First, list the coordinates in order:

  1. ( (-4, 0) )
  2. ( (-1, 0) )
  3. ( (-1, 2) )
  4. ( (2, 2) )
  5. ( (0, 4) )
  6. ( (-4, 0) )

Compute ( \sum x_i y_{i+1} ):

( (-4)(0) + (-1)(2) + (-1)(2) + (2)(4) + (0)(0) = 0 - 2 - 2 + 8 + 0 = 4 )

Compute ( \sum y_i x_{i+1} ):

( (0)(-1) + (0)(-1) + (2)(2) + (2)(0) + (4)(-4) = 0 + 0 + 4 + 0 - 16 = -12 )

Now, the shoelace formula is ( \frac{1}{2} |\sum x_i y_{i+1} - \sum y_i x_{i+1}| )

So ( |4 - (-12)| = 16 ), ( \frac{1}{2} \times 16 = 8 ). Wait, but why the discrepancy? Let's check with another method. Let's use the area of the rectangle plus the area of the triangle above the rectangle. The rectangle is from ( -4,0 ) to ( -1,0 ) to ( -1,2 ) to ( -4,2 ) to ( -4,0 ): area ( 3 \times 2 = 6 ). Then the area above the rectangle: from ( x=-4 ) to ( x=2 ), ( y=2 ) to ( y=4 ), bounded by the two lines: ( y = x + 4 ) (from ( -4,0 ) to ( 0,4 )) and ( y = -x + 4 ) (from ( 2,2 ) to ( 0,4 )). This is a triangle with base from ( x=-4 ) to ( x=2 ), length ( 6 ), and height ( 2 ) (from ( y=2 ) to ( y=4 )), but wait, no, because at ( x=-1 ), the vertical line is at ( y=2 ), so actually, the area above the rectangle is a trapezoid? Wait, no, the shape above the rectangle (from ( y=2 ) to ( y=4 )) is a triangle with vertices at ( (-4,2) ), ( (2,2) ), ( (0,4) ). Wait, ( (-4,2) ) is on the line ( y = x + 4 ) (since ( 2 = -4 + 4 = 0 )? No, ( y = x + 4 ) at ( x