Question

Fie functia f:R-R, f(x)=x(la puterea a doua)-10x+25. Calculati f(5+radical din 7) utilizind formulele inmultirii prescurtate,

Answer 1

f(5+rad7)= (5+rad7)^2-10x(5+rad7)+25=
=5^2+2x5xrad7+rad7^2-50-10rad7+25=
=25+10rad7+7-50-10rad7+25(se reduc +10rad7 cu -10rad7)=
=25+7-50+25=(se reduc 25+25=50 cu -50)
=7

Answer 2

f(x)=(x-5) la puterea a doua deci f(5+rad7)=5+rad7-5 totul la putereava doua deci f este rad7 la puterea a doua adica 7