Task/25752729
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91.2)
(7y -7√6) /(y² -y√6) =7(y -√6)/y(y -√6) = 7/y.
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91.4)
(√23 -s) /(s² -23) =(√23 -s) /(s -√23)(s +√23) = -1/(s +√23) .
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91.6)
( √(2b) -√(2c) ) /(b-c) =√2(√b -√c ) / (√b -√c )(√b +√c ) =√2 / (√b +√c ) .
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92.2)
21/(√7 -y) +3y²/(y -√7) =21/(√7 -y) -3y²/(√7 -y) =(21- 3y²) /(√7 -y) =
3(√7- y)(√7+ y) /(√7 -y) =3(√7+ y).
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92.4)
(15√d) / (√(ab) +√(bc) ) : (30√d) /(a-c) =(15√d) /√b(√a+√c) : (30√d)/(a-c)=
(15√d)* (a-c) / √b(√a +√c) *(30√d) = (a-c) / 2√b(√a +√c) =
(√a -√c)(√a +√c) / 2√b(√a +√c) =(√a -√c)/2√b.