Question

Qual o valor da constante k na função f(x) = kx + 5, de modo que f(-1) + f(2) = 19?

Answer 1

$f(-1)=-k+5\\ f(2)=2k+5\\ \\ f(-1)+f(2)=-k+5+2k+5=19\\ \\ k=19-10\\ \\ \boxed{k=9}$

Answer 2

f(x)=K*x+5
f(-1)=K*-1+5 = -K+5
f(2)=K*2+5 = 2K+5

F(x)= F(-1)+F(2)= 19

f(x)= -K+5+2K+5=19
f(x)= k+10=19
f(x)= k=19-10
f(x)= K=9 

portanto K=9