已知a+1/a=3,则a²+1/a²的值是

已知a+1/a=3,则a²+1/a²的值是
已知a+1/a=3,则a²+1/a²的值是

已知a+1/a=3,则a²+1/a²的值是
a+1/a=3
(a+1/a)²=3²
a²+1/a²+2=9
a²+1/a²=7

a²+1/a² = a²+1/a² + 2 - 2 = a²+1/a² + 2 * a * 1/a - 2 = (a + 1 / a)² - 2 =3^2-2 = 7
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