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Find the area bounded by the curve y=x2+x+4y=x^2+x+4y=x2+x+4​, the x-axis and the ordinates x = 1 and x = 3.
Question

Find the area bounded by the curve y=x2+x+4y=x^2+x+4, the x-axis and the ordinates x = 1 and x = 3.

A.

62/3 units

B.

46 units

C.

65/3 units

D.

61/3 units

Correct option is A

(x2+x+4) dx=x2 dx+x dx+4 dx=x33+x22+4xNow apply the limits from 1 to 3: Step 3: Evaluate the definite integralA=[x33+x22+4x]13At x=3:333+322+4(3)=273+92+12=9+4.5+12=25.5At x=1:133+122+4(1)=13+12+4=2+36+4=56+4=2964.8333 Final Step: SubtractA=25.5296=1536296=1246=623 square units\begin{aligned}&\int (x^2 + x + 4)\,dx = \int x^2\,dx + \int x\,dx + \int 4\,dx = \frac{x^3}{3} + \frac{x^2}{2} + 4x \\[10pt]&\text{Now apply the limits from 1 to 3:} \\[10pt]&{\text{\checkmark\ Step 3: Evaluate the definite integral}} \\[5pt]&A = \left[ \frac{x^3}{3} + \frac{x^2}{2} + 4x \right]_1^3 \\[8pt]&\text{At } x = 3: \\&\quad \frac{3^3}{3} + \frac{3^2}{2} + 4(3) = \frac{27}{3} + \frac{9}{2} + 12 = 9 + 4.5 + 12 = 25.5 \\[10pt]&\text{At } x = 1: \\&\quad \frac{1^3}{3} + \frac{1^2}{2} + 4(1) = \frac{1}{3} + \frac{1}{2} + 4 = \frac{2 + 3}{6} + 4 = \frac{5}{6} + 4 = \frac{29}{6} \approx 4.8333 \\[10pt]&{\text{\checkmark\ Final Step: Subtract}} \\[5pt]&A = 25.5 - \frac{29}{6} = \frac{153}{6} - \frac{29}{6} = \frac{124}{6} = {\frac{62}{3}} \text{ square units}\end{aligned}​​

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