Question

Consideram functia f:R⇒R, F(x)=ax+b.Stiind ca punctele A(2,3) si B(-4,5) sunt situate pe graficul functiei f, calculati f(-1).

Answer 1

2a+b=3
-4a+b=5
inmultim prima ecuatie cu 2

4a+2b=6
-4a+b=5
le adunam
3b=11
b=11/3

2a+11/3=9/3
2a=(9/3)-(11/3)
2a=-2/3
a=(-2/3):2
a=(-2/3)*(1/2)
a=-1/3

ecuatia functiei este $f(x)=- \frac{1}{3}x+ \frac{11}{3}$

$f(-1)=- \frac{1}{3}*(-1)+ \frac{11}{3}= \frac{1}{3}+ \frac{11}{3}= \frac{12}{3}=4$