Question

Se f(2) = 5 e f(3) = -10, a função f(x) = ax + b será dada por:

y = - 15x + 35.

y = 15x - 35.

y = - 10x + 30

y = 20x + 35.

y = - 15x + 45.

Answer 1

$f(x)=ax+b$

$f(2)=5~\Rightarrow~2a+b=5~(i)$

$f(3)=-10~\Rightarrow~3a+b=-10~(ii)$

Fazendo (ii) - (i):

$3a+b-2a-b=-10-5$

$a=-15$

$2a+b=5$

$2\cdot(-15)+b=5$

$-30+b=5$

$b=35$

$f(x)=-15x+35$