Ответ:

Объяснение:

5x^2+9x-18=0

Найти 1/x1+1/x2;   (x1)^2+(x2)^2

По т. Виета

x1+x2 = -9/5;

x1*x2=-18/5;

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(x1+x2)^2=(-9/5)^2 = 81/25;

(x1+x2)^2 = x1^2+2x1*x2 + (x2)^2= (x1^2+x2^2) + 2x1*x2=81/25;

(x1^2+x2^2)=81/25 - 2*(-18/5) = 81/25+36/5=10,44.

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1/x1+1/x2 = (x1+x2)/(x1*x2)=(-9/5) / (-18/5) = 9/5 * 5/18 = 1/2.