26. If \[ \int_{-2}^{6} f(x)\,dx = 10 \quad \text{and} \quad \int_{2}^{6} f(x)\,dx = 3, \] then \[ \int_{2}^{6} f(4 - x)\,dx = \ ? \]






Answer is: option3

7

Solution:

Given Information:

  1. \(\int_{-2}^{6} f(x)\,dx = 10\)
  2. \(\int_{2}^{6} f(x)\,dx = 3\)

Find \(\int_{-2}^{2} f(x)\,dx\):

\[ \int_{-2}^{6} f(x)\,dx = \int_{-2}^{2} f(x)\,dx + \int_{2}^{6} f(x)\,dx \] \[ 10 = \int_{-2}^{2} f(x)\,dx + 3 \] \[ \int_{-2}^{2} f(x)\,dx = 10 - 3 = 7 \]

Evaluate \(\int_{2}^{6} f(4 - x)\,dx\):

Let's perform a substitution: \( u = 4 - x \Rightarrow du = -dx \Rightarrow dx = -du \)

  1. When \(x = 2\), \(u = 4 - 2 = 2\)
  2. When \(x = 6\), \(u = 4 - 6 = -2\)

\[ \int_{2}^{6} f(4 - x)\,dx = \int_{2}^{-2} f(u)(-du) = \int_{-2}^{2} f(u)\,du \]

We already found that \(\int_{-2}^{2} f(u)\,du = 7\)

\[ \int_{2}^{6} f(4 - x)\,dx = 7 \]

Option C

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