Question

Daca f(x)=-2x+1/2 calculati S=f(1)+f(3)+f(5)+...+f(99)

Answer 1

ptr. f(x) = -2x + 1/2
f(1) = - 3/2
f(3) = -11 /2
f(5) = - 19/2
f(7) = - 27/2
....................
f(99) = - 395/2
S = - 1/2 (3+11+19+27+......+395) = - 1/2[ (3+0·8) +(3+1·8)+(3+2·8)+......+(3+49·8)]
= - 1/2 [3·50 + 8(1+2+3+......+49)] = - 1/2[150+ 8·49·50/2] = - 1/2(150+9800) =
= - 4975