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# questions (in confusion)

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9. Let $$f(x) = 2x + 7$$ and $$g(x) = 3x + c$$ . Find c if $$f(g(x)) = g(f(x))$$ for all .

10. The function f(x) satisfies

$$f(\sqrt{x + 1}) = \frac{1}{x}$$
for all $$x \ge -1,$$ $$x\neq 0.$$ Find f(2).

11. Let $$f(x) = 3x^2 - 4x$$. Find the constant k such that $$f(x) = f(k - x)$$ for all real numbers x .

Feb 25, 2019
edited by Guest  Feb 25, 2019
edited by Guest  Feb 25, 2019

### 2+0 Answers

#1
+19686
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9.     f (gx) = g (fx)

2 (3x+c) + 7      = 3(2x+7) = c

6x + 2c   + 7     =  6x + 21 + c

c = 14

Feb 25, 2019
#2
+104627
+1

10.   f(2)   =  f ( √( x + 1] )    implies that

√ [ x + 1 ]  =  2   square both sides

x + 1 =  4

x = 3

So

f(2)  =  1/3

Feb 25, 2019