Question

F(x) = 3x + 5
Work out a if f(a)= -13

Answer 1

a = - 6

Explanation:

Given

f(x) = 3x + 5 , then

f(a) = 3a + 5 and f(a) = - 13 , then equating the right sides

3a + 5 = - 13 ( subtract 5 from both sides )

3a = - 18 ( divide both sides by 3 )

a = - 6

Answer 2

a = -6

Explanation:

see, x has been replaced by a.

so f(a) = 3a + 5 . . . . . . . (i)

a displaces x from it's every position in the equation.

and it's given that f(a) = -13

putting f(a) = -13 in equation (i) :-

3a + 5 = -13

• taking like terms to one side

3a = -18

• dividing the equation by 3

`\blue{ \implies}\mathfrak { \red { \underline{ \: a = - 6 } } }`