Question

Se considera functia f: R ➡R , f (x ) = 3x-5.
A) calculati suma S=f (1) +f(2)+...+f(10).
B) calculati produsul P= f (1 supra 3) x f (2 supra 3) x ... f (10 supra 3 ).

Answer 1

a)
[tex]S=(3*1-5)+(3*2-5)+(3*3-5)+...+(3*10-5)\\ S=3*1+3*2+...+3*10-5*10\\ S=3(1+2+...+10)-50\\ S=3* \frac{10*11}{2}-50=115 [/tex]

b)
[tex]P=(3* \frac{1}{3}-5 )(3* \frac{2}{3}-5 )...(3* \frac{10}{3}-5 )\\ P=(1-5)(2-5)(3-5)...(10-5)\\ P=(-4) * (-3) * (-2) *(-1)*0* ... * 5=0[/tex]