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mathsssssss~!!
發問:
a^2 - b^2 = -16 ab=15 求a, b~ 更新: 我要埋條式~~ 唔該晒
最佳解答:
a^2 - b^2 = -16………(1) ab=15…….(2) From (2) a = 15/b………(3) Substitute (3) into (1) (15/b)^2 – b^2 = -16 225/b^2 – b^2 = -16 225 – b^4 = -16b^2 b^4 – 16b^2 – 225 = 0 (b^2 – 25)(b^2 + 9) = 0 b^2 = 25 or b^2 = -9 (rejected because b^2 must >= 0) b = 5 or -5 when b=5, a = 15/5 = 3 when b=-5, a = 15/-5 = -3 Therefore a=3 and b=5 Or a=-3 and b=-5
a=3, b=5|||||a=15/b a^2=225/b^2 225/b^2-b^2=-16 16=(b^2-225)b^2 16b^2=b^2-225 15b^2=-225 b^2=-15 no solution|||||a=3 b=5
mathsssssss~!!
發問:
a^2 - b^2 = -16 ab=15 求a, b~ 更新: 我要埋條式~~ 唔該晒
最佳解答:
a^2 - b^2 = -16………(1) ab=15…….(2) From (2) a = 15/b………(3) Substitute (3) into (1) (15/b)^2 – b^2 = -16 225/b^2 – b^2 = -16 225 – b^4 = -16b^2 b^4 – 16b^2 – 225 = 0 (b^2 – 25)(b^2 + 9) = 0 b^2 = 25 or b^2 = -9 (rejected because b^2 must >= 0) b = 5 or -5 when b=5, a = 15/5 = 3 when b=-5, a = 15/-5 = -3 Therefore a=3 and b=5 Or a=-3 and b=-5
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其他解答:a=3, b=5|||||a=15/b a^2=225/b^2 225/b^2-b^2=-16 16=(b^2-225)b^2 16b^2=b^2-225 15b^2=-225 b^2=-15 no solution|||||a=3 b=5
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