Post

Created by @nathanedwards
 at November 1st 2023, 4:48:54 pm.

Question:

Let f(x)=x23xf(x) = x^2 - 3x and g(x)=2x1g(x) = 2x - 1 be two functions defined for 0x40 \leq x \leq 4. Find the area of the region bounded by the curves f(x)f(x) and g(x)g(x).

Answer:

To find the area of the region bounded by the curves f(x)f(x) and g(x)g(x), we need to determine the points of intersection between the two curves first.

Setting f(x)=g(x)f(x) = g(x), we have:

x23x=2x1x^2 - 3x = 2x - 1

Simplifying the equation, we get:

x25x+1=0x^2 - 5x + 1 = 0

We can solve this quadratic equation by factoring or using the quadratic formula. However, upon inspection, we can see that there are no real solutions for this equation. Thus, the curves f(x)f(x) and g(x)g(x) do not intersect in the given interval 0x40 \leq x \leq 4.

Therefore, the area bounded by the curves is equal to the area under f(x)f(x) minus the area under g(x)g(x).

Let's first find the area under f(x)f(x):

Af=04f(x)dxA_{f} = \int_{0}^{4} f(x) \, dx
Af=04(x23x)dxA_{f} = \int_{0}^{4} (x^2 - 3x) \, dx

Using the power rule of integration, we can integrate term by term:

Af=[13x332x2]04A_{f} = \left[ \frac{1}{3} x^3 - \frac{3}{2} x^2 \right]_{0}^{4}
Af=(13433242)(13033202)A_{f} = \left( \frac{1}{3} \cdot 4^3 - \frac{3}{2} \cdot 4^2 \right) - \left( \frac{1}{3} \cdot 0^3 - \frac{3}{2} \cdot 0^2 \right)
Af=(13643216)(00)A_{f} = \left( \frac{1}{3} \cdot 64 - \frac{3}{2} \cdot 16 \right) - \left( 0 - 0 \right)
Af=643482A_{f} = \frac{64}{3} - \frac{48}{2}
Af=64324A_{f} = \frac{64}{3} - 24
Af=643723A_{f} = \frac{64}{3} - \frac{72}{3}
Af=83A_{f} = -\frac{8}{3}

Next, let's find the area under g(x)g(x):

Ag=04g(x)dxA_{g} = \int_{0}^{4} g(x) \, dx
Ag=04(2x1)dxA_{g} = \int_{0}^{4} (2x -1) \, dx

Again, we can integrate term by term:

Ag=[x2x]04A_{g} = \left[ x^2 - x \right]_{0}^{4}
Ag=(424)(020)A_{g} = (4^2 - 4) - (0^2 - 0)
Ag=(164)(00)A_{g} = (16 - 4) - (0 - 0)
Ag=12A_{g} = 12

Now, we can find the area bounded by the curves:

Area=AfAg\text{Area} = A_{f} - A_{g}
Area=8312\text{Area} = -\frac{8}{3} - 12
Area=83363\text{Area} = -\frac{8}{3} - \frac{36}{3}
Area=443\text{Area} = -\frac{44}{3}

Therefore, the area of the region bounded by the curves f(x)f(x) and g(x)g(x) is 443-\frac{44}{3} square units.