Răspuns:
Explicație pas cu pas:
a)
x² + 1/x² = ?
( x + 1/x)² = 3²
x² + 2 x/x + 1/x² = 9
x² + 1/x² = 9 - 2
x + 1/x² = 7
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b)
x² - 1/x² = ( x - 1/x ) ( x + 1/x ) = 3 × √5 = 3√5
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c)
x³ - 1/x³ = ( x - 1/x ) ( x² + x/x + 1/x² ) = √5 × 8= 8√5
x² +x/x + 1/x² = (x²+1/x²) + 1 = 7+1=8
