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Evaluating a polynomial definite integral via FTC Part 2

Evaluate the definite integral: ∫12(5x4−3x2+2) dx\int_1^2 (5x^4 - 3x^2 + 2)\, dx

Hint

Find an antiderivative F(x)F(x) of the integrand term by term, then compute F(2)−F(1)F(2) - F(1).

Step-by-step solution

First find an antiderivative of each term. Since ∫5x4 dx=x5\int 5x^4\,dx = x^5, ∫3x2 dx=x3\int 3x^2\,dx = x^3, and ∫2 dx=2x\int 2\,dx = 2x, an antiderivative of the integrand is F(x)=x5−x3+2xF(x) = x^5 - x^3 + 2x. By FTC Part 2, ∫12(5x4−3x2+2) dx=F(x)∣12=F(2)−F(1)\int_1^2 (5x^4-3x^2+2)\,dx = F(x)\Big|_1^2 = F(2) - F(1).

Now evaluate: F(2)=25−23+2(2)=32−8+4=28F(2) = 2^5 - 2^3 + 2(2) = 32 - 8 + 4 = 28, and F(1)=15−13+2(1)=1−1+2=2F(1) = 1^5 - 1^3 + 2(1) = 1 - 1 + 2 = 2. Therefore the integral equals F(2)−F(1)=28−2=26F(2) - F(1) = 28 - 2 = 26.

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