Question

Calculati f(1)+f(2)+f(3)+f(4)+f(5) daca f:R-R si a) f(x)=3; b) f(x)=-3; c) f(x)=2x; d) f(x)=x +7

Answer 1

Răspuns:

Explicație pas cu pas:

S=f(1)+f(2)+f(3)+f(4)+f(5)=?  f:R⇒R

a) f(x)=3⇒ f(1)=f(2)=f(3)=f(4)=f(5)=3    ⇒S=3×5=15

b) f(x)=-3 ⇒f(1)=f(2)=f(3)=f(4)=f(5)=-3   ⇒S=(-3)×5=-15

c)f(x)=2x  ⇒f(1)+f(2)+f(3)+f(4)+f(5)=2+4+6+8+10=2(1+2+3+4+5)=2×5×6/2=30

d)f(x)=x+7  ⇒f(1)+f(2)+f(3)+f(4)+f(5)=1+2+3+4+5+5×7=5×6/2+35=15+35=50