Răspuns:
Explicație pas cu pas:
21.
a - b = 4
a^2 - b^2 = 24
a^2 - b^2 = (a - b)(a + b)
4(a + b) = 24
a + b = 24 : 4 = 6
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22.
a + b = 4
a*b = 2
(a + b)/a*b = 4/2
a/a*b + b/a*b = 2
1/b + 1/a = 2
_________________
23.
a + b = 4
a*b = 2
(a + b)^2 = 16
a^2 + 2a*b + b^2 = 16
a^2 + 2 + b^2 = 16
a^2 + b^2 = 16 - 2 = 14
___________________
24.
x - 1/x = 2
(x - 1/x)^2 = 4
x^2 + 2*x*1/x + 1/x^2 = 4
x^2 + 1/x^2 = 4 - 2 = 2
____________________
25.
a - b = 1
a^2 + b^2 - 2ab + 2a - 2b + 1 = (a - b)^2 + 2(a - b) + 1 = 1 + 2 + 1 = 4
