1.√320/6561
2.√25a^2-7^2
3.√6^2+8^2
4.√7/12+1/9
5.-√12^2-9^2
(F2)二次根式
2007-09-19 1:28 am
回答 (2)
2007-09-19 2:49 am
如果根號係包括晒成條式，你應該用括號括往
1.√(320/6561)
=√320/√6561
=8√5 ÷ 81
=8√5 ×1/ 81
= 8√5 / 81
2.√(25a2﹣72)
= (√25a)2﹣(√7)2
= 5a﹣7
3.√(62+82)
= (√6)2+ (√8)2
= 6+8
=14
4.√(7/12+1/9)
=√(7/12) + √(1/9)
=√7 /√12 + √1/ √9
= √7 /2√3 + 1/ 3
= (3√7 + 1) /6√3
= (3√7 + 1) /6√3 × 6√3/6√3
= 6√3(3√7 + 1) /6(√3)2
= 18√21 / 18
= √21
5. ﹣√(122﹣92)
= ﹣(√12)2+(√9)2
= ﹣12+9
= -3
1.√(320/6561)
=√320/√6561
=8√5 ÷ 81
=8√5 ×1/ 81
= 8√5 / 81
2.√(25a2﹣72)
= (√25a)2﹣(√7)2
= 5a﹣7
3.√(62+82)
= (√6)2+ (√8)2
= 6+8
=14
4.√(7/12+1/9)
=√(7/12) + √(1/9)
=√7 /√12 + √1/ √9
= √7 /2√3 + 1/ 3
= (3√7 + 1) /6√3
= (3√7 + 1) /6√3 × 6√3/6√3
= 6√3(3√7 + 1) /6(√3)2
= 18√21 / 18
= √21
5. ﹣√(122﹣92)
= ﹣(√12)2+(√9)2
= ﹣12+9
= -3
2007-09-19 1:41 am
唔明你呢d→^ 點解???
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https://hk.answers.yahoo.com/question/index?qid=20070918000051KK02019