SOLUTION: Find the area of the region bounded by functions: {{{ f(x)= -x^2 + 3x }}} and {{{ g(x) = 2x^3 - x^2 - 5x }}}

Algebra ->  Trigonometry-basics -> SOLUTION: Find the area of the region bounded by functions: {{{ f(x)= -x^2 + 3x }}} and {{{ g(x) = 2x^3 - x^2 - 5x }}}      Log On


   



Question 934217: Find the area of the region bounded by functions:
+f%28x%29=+-x%5E2+%2B+3x+ and +g%28x%29+=+2x%5E3+-+x%5E2+-+5x+

Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
system%28%22f%28x%29%22=+-x%5E2+%2B+3x%2C+%22g%28x%29%22=2x%5E3+-+x%5E2+-+5x%29
We find where the two curves intersect by setting them equal

-x%5E2+%2B+3x=2x%5E3+-+x%5E2+-+5x
0=2x%5E3-8x
2x%5E3-8x=0
x%5E3-4x=0
x%28x%5E2-4%29=0
x%28x-2%29%28x%2B2%29=0
Three solutions (points of intersection):
x=0; x-2=0; x+2=0
x=2; x=-2
The curves intersect at (-2,-10), (0,0), (2,2)

As we see, there are two loops bound by these curves.
We must find the areas of the two loops separately, because
the upper curve in the left loop is the lower curve in the
loop on the right.


Area%22%22=%22%22
Left loop:
int%28%28%282x%5E3-x%5E2-5x%29-%28-x%5E2+%2B+3x%29%5E%22%22%29%2Cdx%2C-2%2C0%29%22%22=%22%22
int%28%282x%5E3-x%5E2-5x%2Bx%5E2+-+3x%29%2Cdx%2C-2%2C0%29%22%22=%22%22
int%28%282x%5E3-8x%29%2Cdx%2C-2%2C0%29%22%22=%22%22
%22%22=%22%22%280%5E4%2F2-4%2A0%5E2%29-%28%28-2%29%5E4%2F2-4%2A%28-2%29%5E2%29+%22%22=%22%228
Right loop:
int%28%28%28-x%5E2+%2B+3x%29-%282x%5E3-x%5E2-5x%29%5E%22%22%29%2Cdx%2C0%2C2%29%22%22=%22%22
int%28%28-x%5E2%2B3x-2x%5E3%2Bx%5E2%2B5x%29%2Cdx%2C0%2C2%29%22%22=%22%22
int%28%28-2x%5E3%2B8x%29%2Cdx%2C0%2C2%29%22%22=%22%22
%22%22=%22%22%28-%282%29%5E4%2F2%2B4%2A%282%29%5E2%29%28-0%5E4%2F2%2B4%2A0%5E2%29+%22%22=%22%228
Total area = 8+8 = 16
Edwin