Question

If f(x) = 3x - 1 and 2f(b) = 28, what is the value of f(2b)?

Answer 1

Answer:  29

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Work Shown:

Solve the second equation for f(b)

2f(b) = 28

f(b) = 28/2

f(b) = 14

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Plug in x = b and solve for b

f(x) = 3x-1

f(b) = 3b-1 ... replace every x with b

14 = 3b-1 ..... plug in f(b) = 14

3b-1 = 14

3b = 14+1

3b = 15

b = 15/3

b = 5

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f(x) = 3x-1

f(2b) = 3(2b)-1 .... replace every x with 2b

f(2b) = 3(2*5)-1 .... plug in b = 5

f(2b) = 3*10-1

f(2b) = 30-1

f(2b) = 29