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標題:

quadratic formula 2 (urgent)

發問:

1. 1/6 (x^2 +18=4) 2. 5x(x-3)+4(x+4)=31-7x^2 it must use quadratic formula to solve it,thx~

• 30年內，A君所賺的錢較多，還是B君所賺的錢較多﹖_0
• 26"LCD TV
• 我想買一套寫作系列既書,但唔記得書名@1@

• 30年內，A君所賺的錢較多，還是B君所賺的錢較多﹖_0
• 26"LCD TV
• 我想買一套寫作系列既書,但唔記得書名@1@

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最佳解答:

#001, use quadratic formula!!! 1) (x^2 + 18) / 6 = 4 x^2 + 18 = 24 x^2 - 6 = 0 x = 0 +- sqrt(24) / 2 = 0 +- 2sqrt6 / 2 = 0 +- sqrt6 = sqrt6 or -sqrt6 2) 5x(x - 3) + 4(x + 4) = 31 - 7x^2 5x^2 - 15x + 4x + 16 = 31 - 7x^2 12x^2 - 11x - 15 = 0 x = 11 +- sqrt(121 + 720) / 24 = 11 +- sqrt29 / 24 = (11 + sqrt29) / 24 or (11 - sqrt29) / 24

其他解答:

第1題點解會括埋個=既? 係咪 1/6(x^2+18) = 4? 如果係的話.. x^2 + 18 = 24 x^2 = 6 x = (+/-)開方6 #2 5x(x-3) + 4(x+4) = 31-7x^2 5x^2 - 15x + 4x + 16 = 31 - 7x^2 12x^2 - 11x - 15 = 0 (3x - 5)(4x + 3) = 0 x = 5/3 or -3/4 有錯sorry話我知