13). a/b = 3/4, de unde a = 3b/4
a+b=3/4, inlocuim pe a in functie de b:
3b/4 + b = 3/4, se aduce la acelasi numitor:
3b + 4b = 3, rezulta b = 3/7
a = 3/7 * 3/4 = 9/28
Media aritmetica = (3/7 + 9/28) ÷ 2 = 3/4 ÷ 2 = 3/8.
Media geometrica = √(9/28 * 3/7) = √(21/196) = √21 / 14.
14). c/d = 2/5, de unde c = 2d/5
c+d=2/5, inlocuim pe c in functie de d:
2d/5 + d = 2/5, se aduce la acelasi numitor:
7d=2, rezulta d=2/7
c = 2/7 * 2/5 = 4/35
Media aritmetica = (2/7 + 4/35) ÷ 2 = 2/5 ÷ 2 = 2/10 = 1/5
Media geometrica = √(4/35 * 2/7) = √(8/245) = 2√2 / 7√5
= 2√10 / 35