Monday, October 10, 2016

If the integral from 1 to 4 of f(x)=7, then what does the integral from 1 to 4 of 2f(x)+5=?

`int_1^4 f(x) dx= 7`


Find `int_1^4 (2f(x) + 5)dx` .


To solve, express this as sum of two integrals.


`int_1^4 (2f(x) + 5)dx`


`=int_1^4 2f(x) dx + int_1^4 5dx`


Then, factor out the 2 in the first integral.


`= 2int_1^4 f(x) dx + int_1^4 5dx`


Plug-in the given `int_1^4 f(x) dx= 7` .


`=2(7) + int_1^4 5 dx`


`= 14 + int_1^4 5 dx`


For the second integral, apply the formula int c dx = cx.


`= 14 + 5x|_1^4`


To evaluate the definite integral, apply the formula `int_a^b f(x) dx = F(b) - F(a)` .


`= 14 + (5*4 - 5*1)`


`=14 + 15`


`= 29`



Therefore,  `int_1^4 (2f(x) + 5)dx = 29` .

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