Math  /  Geometry

QuestionFind the area of the region bound by the following equations: y=6x+6,y=0,x=3 and x=7y=6 x+6, \quad y=0, \quad x=3 \text { and } x=7

Studdy Solution

STEP 1

What is this asking? We need to find the area under the line y=6x+6y = 6x + 6 between x=3x = 3 and x=7x = 7, and above the x-axis (y=0y=0). Watch out! Don't forget that we're looking for an *area*, so our answer should always be positive!

STEP 2

1. Define the integral
2. Calculate the integral
3. Evaluate the boundaries

STEP 3

Alright, let's **set up our integral**!
We're looking for the area under the curve y=6x+6y = 6x + 6, so we'll integrate this function.
Our **boundaries** are from x=3x = 3 to x=7x = 7, so our integral looks like this: 37(6x+6)dx \int_{3}^{7} (6x + 6) \, dx This integral represents the **area** we're trying to find!

STEP 4

Time to **calculate the integral**!
Remember the power rule for integration: xndx=xn+1n+1+C\int x^n \, dx = \frac{x^{n+1}}{n+1} + C.
Don't forget the constant of integration, CC, even though it will disappear when we evaluate the definite integral.

STEP 5

Applying the power rule, the integral of 6x6x is 6x22=3x2\frac{6x^2}{2} = 3x^2.
The integral of 66 is 6x6x.
So, our **integrated expression** is: 3x2+6x+C 3x^2 + 6x + C

STEP 6

Now, let's **evaluate** our result at the **upper and lower limits** of integration.
We plug in x=7x = 7 (the **upper limit**) and subtract the result when we plug in x=3x = 3 (the **lower limit**).

STEP 7

Plugging in x=7x = 7, we get: 3(7)2+6(7)+C=3(49)+42+C=147+42+C=189+C 3(7)^2 + 6(7) + C = 3(49) + 42 + C = 147 + 42 + C = 189 + C Plugging in x=3x = 3, we get: 3(3)2+6(3)+C=3(9)+18+C=27+18+C=45+C 3(3)^2 + 6(3) + C = 3(9) + 18 + C = 27 + 18 + C = 45 + C

STEP 8

Finally, subtract the **lower limit result** from the **upper limit result**: (189+C)(45+C)=189+C45C=18945=144 (189 + C) - (45 + C) = 189 + C - 45 - C = 189 - 45 = 144 Notice how the constant of integration, CC, cancels out!
This always happens with definite integrals.

STEP 9

The area of the region is **144 square units**!

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