Question

Let f be a function from R to R defined by
f (x) = 3x − 5 . Find the values of a and b given that (a, 4) and (1, b) $\in$ f.

• A. a = 3 and b = 2
• B. a = 3 and b = -2
• C. a = -3 and b = -2
• D. a = -3 and b = 2

Answer 1

The correct option is B a = 3 and b = -2

Here, (a, 4) means the image of a is 4.
i.e. f (a) = 4
$\Rightarrow$ 3a – 5 = 4
$\Rightarrow$ a = 3
Also,
(1, b) means the image of 1 is b.
i.e. f (1) =b
$\Rightarrow$ 3(1) - 5 = b
$\Rightarrow$ b = −2
$\therefore$ a = 3 and b = -2