If 9 f(x) dx = 35 0 and 9 g(x) dx = 14, 0 find 9 [3f(x) + 4g(x)] dx

For this problem you need to know that the derivative is an associative operation, so f(x)dx+g(x)dx=[f(x)+g(x)]dx.
start by solving your two equations for f(x)dx and g(x)dx. this gets you
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now you can change your equation you need to evaluate into something you can evaluate, using the property I explained to start.
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now you know the values of f(x)dx and g(x)dx, so you can plug those in