Răspuns:
7. 2² : 2ˣ= 2⁴ 2ˣ= 2²:2⁴ 2ˣ=1/4 x= -2
7. a) (1+3+5+7+...+21) -2(1+2+3+...+11)= aplicam suma gauss
(21+1) *11 :2 - 2*11*12 :2 = 11*11- 11*12= 11*(11-12) = 11*(-1)= -11
b) (1+4+5+ 8+9+12 +...+ 61+64) - ( 2+3 +6+7+10+11 +....+62+63)
= 1 +(4-2) +(5-3) +(8-6) +(9-7) +(12-10) + (13-11) +...+ (61-62) +(64-63)=
= 1+ 2+2 +2 +2 +2+2 +...+2- 63 = 1+2*30+2- 63= 63-63=0
