Question

Guess the rule of linear relation for the given mapping diagram.

• A. $y=7x-20$
• B. $y=20-7x$

Answer 1

The correct option is B $y=20-7x$

Let the rule for the linear relation be $y=ax+c$
For $x=0,y=c$

From the mapping diagram,

$0$ is mapped to $20.$
$\therefore y=c=20$
$\Rightarrow y=ax+20$

Similarly, for $x=-1.y=a(-1)+20=-a+20$
From mapping diagram,
$-1$ is mapped to $27.$
$\therefore y=-a+20=27$
$\Rightarrow -a=7$
$\Rightarrow a=-7$

$\therefore$ The required function is $y=-7x+20.$