Determine whether the following statements are true and give an explanation or counterexample.
c. ∫₀¹(x−x^2) dx=∫₀¹(√y−y) dy
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Step 1: Begin by analyzing the given integral expressions. The first integral is ∫₀¹(x − x²) dx, which is in terms of x, and the second integral is ∫₀¹(√y − y) dy, which is in terms of y. To determine if these are equal, we need to explore whether a relationship exists between the two integrals.
Step 2: Recognize that the equality of these integrals might depend on a change of variables. Specifically, check if there is a substitution that transforms the integral in terms of x into the integral in terms of y. For example, consider the substitution y = x², which relates x and y.
Step 3: Apply the substitution y = x². If y = x², then dy = 2x dx. Also, note that when x ranges from 0 to 1, y will range from 0 to 1 as well. Substitute these relationships into the integral ∫₀¹(x − x²) dx to see if it matches the form of ∫₀¹(√y − y) dy.
Step 4: Rewrite the integral ∫₀¹(x − x²) dx using the substitution y = x². Replace x with √y and dx with dy/2x (or dy/(2√y)). Carefully simplify the resulting integral and compare it to ∫₀¹(√y − y) dy.
Step 5: Conclude whether the two integrals are equal based on the substitution and simplification. If the substitution leads to the second integral exactly, the statement is true. If not, provide a counterexample or explanation showing why the integrals differ.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Definite Integrals
A definite integral represents the signed area under a curve between two specified limits. It is denoted as ∫_a^b f(x) dx, where 'a' and 'b' are the lower and upper limits, respectively. The value of a definite integral can be computed using the Fundamental Theorem of Calculus, which connects differentiation and integration.
Substitution is a technique used in integration to simplify the process by changing the variable of integration. This method involves replacing a variable with another variable that simplifies the integral, making it easier to evaluate. For example, if y = g(x), then dy = g'(x) dx, allowing the integral to be expressed in terms of y.
Comparing integrals involves evaluating whether two integrals yield the same value. This can be done by transforming one integral into another through substitution or by analyzing the functions involved. In the given statement, one must determine if the areas represented by the two integrals are equal, which may require evaluating both integrals separately.