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The value of ∫−55∣x+3∣dx\int_{-5}^{5} |x + 3| dx is

Solution

✅ Correct Option: 3

The absolute value ∣x+3∣|x + 3| changes definition at x=−3x = -3:

When x<−3x < -3: ∣x+3∣=−x−3|x + 3| = -x - 3

When x≥−3x \geq -3: ∣x+3∣=x+3|x + 3| = x + 3


Since the function changes at x=−3x = -3, the integral must be split:

∫−55∣x+3∣dx=∫−5−3∣x+3∣dx+∫−35∣x+3∣dx\int_{-5}^{5} |x + 3| dx = \int_{-5}^{-3} |x + 3| dx + \int_{-3}^{5} |x + 3| dx


For −5≤x<−3-5 \leq x < -3, we have ∣x+3∣=−x−3|x + 3| = -x - 3:

∫−5−3(−x−3)dx=[−x22−3x]−5−3\int_{-5}^{-3} (-x - 3) dx = \left[-\frac{x^2}{2} - 3x\right]_{-5}^{-3}

At x=−3x = -3:

−(−3)22−3(−3)=−92+9=92-\frac{(-3)^2}{2} - 3(-3) = -\frac{9}{2} + 9 = \frac{9}{2}

At x=−5x = -5:

−(−5)22−3(−5)=−252+15=52-\frac{(-5)^2}{2} - 3(-5) = -\frac{25}{2} + 15 = \frac{5}{2}

Result: 92−52=2\frac{9}{2} - \frac{5}{2} = 2


For −3≤x≤5-3 \leq x \leq 5, we have ∣x+3∣=x+3|x + 3| = x + 3:

∫−35(x+3)dx=[x22+3x]−35\int_{-3}^{5} (x + 3) dx = \left[\frac{x^2}{2} + 3x\right]_{-3}^{5}

At x=5x = 5:

(5)22+3(5)=252+15=552\frac{(5)^2}{2} + 3(5) = \frac{25}{2} + 15 = \frac{55}{2}

At x=−3x = -3:

(−3)22+3(−3)=92−9=−92\frac{(-3)^2}{2} + 3(-3) = \frac{9}{2} - 9 = -\frac{9}{2}

Result: 552−(−92)=552+92=32\frac{55}{2} - \left(-\frac{9}{2}\right) = \frac{55}{2} + \frac{9}{2} = 32


Total: 2+32=342 + 32 = 34

Therefore, ∫−55∣x+3∣dx=34\int_{-5}^{5} |x + 3| dx = 34

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