Chapter 6: Problem 23
Find the integrals .Check your answers by differentiation. $$\int y^{2}(1+y)^{2} d y$$
Short Answer
Expert verified
The integral is \( \frac{y^3}{3} + \frac{y^4}{2} + \frac{y^5}{5} + C \).
Step by step solution
01
Expand the Expression
First, we need to expand the expression \( y^2 (1+y)^2 \). This requires us to expand \( (1+y)^2 \). The expanded form of \( (1+y)^2 \) is \( 1 + 2y + y^2 \).Then, multiply the expanded expression by \( y^2 \):\[ y^2 (1 + 2y + y^2) = y^2 + 2y^3 + y^4 \].
02
Integrate Each Term Separately
The integral we need to solve is now \( \int (y^2 + 2y^3 + y^4) \, dy \).We integrate each term:\( \int y^2 \, dy = \frac{y^3}{3} + C_1 \)\( \int 2y^3 \, dy = \frac{2y^4}{4} = \frac{y^4}{2} + C_2 \)\( \int y^4 \, dy = \frac{y^5}{5} + C_3 \).
03
Combine the Integrals
Combine all the integrated terms:\[ \frac{y^3}{3} + \frac{y^4}{2} + \frac{y^5}{5} + C \] where \( C = C_1 + C_2 + C_3 \) is the constant of integration.
04
Differentiate to Verify the Solution
Differentiate the obtained solution to ensure it matches the original integrand:Differentiating \( \frac{y^3}{3} + \frac{y^4}{2} + \frac{y^5}{5} \), we get:\( \frac{d}{dy} \left( \frac{y^3}{3} \right) = y^2 \)\( \frac{d}{dy} \left( \frac{y^4}{2} \right) = 2y^3 \)\( \frac{d}{dy} \left( \frac{y^5}{5} \right) = y^4 \)Combining these derivatives results in the original expression: \[ y^2 + 2y^3 + y^4 \], confirming the solution is correct.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Expansion
When faced with an expression like \( y^2 (1+y)^2 \), one efficient way to handle it is through polynomial expansion. Polynomial expansion allows us to convert a complex polynomial into a simpler form. This makes it easier to integrate each term separately.
Consider the expression \((1+y)^2\), which is a binomial. By applying the binomial expansion formula, we get:
Consider the expression \((1+y)^2\), which is a binomial. By applying the binomial expansion formula, we get:
- \((1+y)^2 = 1 + 2y + y^2\).
- \(y^2(1+2y+y^2) = y^2 + 2y^3 + y^4\).
Differentiation
Differentiation is an essential concept in calculus, allowing us to find the derivative of a function, which represents the rate of change of a function with respect to a variable. In this exercise, after integrating the expression, differentiation is used to verify our solution.
Once we have integrated the polynomial and obtained the expression:
Once we have integrated the polynomial and obtained the expression:
- \(\frac{y^3}{3} + \frac{y^4}{2} + \frac{y^5}{5}\),
- The derivative of \(\frac{y^3}{3}\) is \(y^2\),
- The derivative of \(\frac{y^4}{2}\) is \(2y^3\),
- The derivative of \(\frac{y^5}{5}\) is \(y^4\).
Integral Calculus
Integral calculus is concerned with the accumulation of quantities and the areas under and between curves. A vital concept is the indefinite integral, which involves finding a function whose derivative is the given function.
In our exercise, the task was to integrate \(y^2 + 2y^3 + y^4\). Integrating each term separately, we find:
In our exercise, the task was to integrate \(y^2 + 2y^3 + y^4\). Integrating each term separately, we find:
- \(\int y^2 \, dy = \frac{y^3}{3}\),
- \(\int 2y^3 \, dy = \frac{y^4}{2}\),
- \(\int y^4 \, dy = \frac{y^5}{5}\).
- \(\frac{y^3}{3} + \frac{y^4}{2} + \frac{y^5}{5} + C\).