utefdxd的部落格

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maths

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發問:

1. ax-ay+cx-cy 3. a2+ab+ac+b 5. 5ab-3c-3ac+5b 7. s2-st+2t2-2st 9. 9t2-16 11. 26b-169-b2 13. 50x2-80xy+32y2 15. 8m3-125 請注意紅色的是指數!!!

最佳解答:

1. ax-ay+cx-cy = a(x-y)+c(x-y) = (a+c)(x-y) 3. 我猜這題目應該是: a^2+ab+ac+bc = a(a+b)+c(a+b) = (a+c)(a+b) 5. 5ab-3c-3ac+5b = 5ab+5b-3ac-3c = 5b(a+1)-3c(a+1) = (5b-3c)(a+1) 7. s^2-st+2t^2-2st = s^2-st-2st+2t^2 = s(s-t)-2t(s-t) = (s-2t)(s-t) 9. 9t^2-16 = (3t)^2-4^2 = (3t-4)(3t+4) 11. 26b-169-b^2 = -(b^2-26b+169) = -(b^2-2(b)(13)+13^2) = -(b-13)^2 13. 50x^2-80xy+32y^2 = 2(25x^2-40xy+16y^2) = 2((5x)^2-2(5x)(4y)+(4y)^2) = 2(5x-4y)^2 15. 8m^3-125 = (2m)^3-5^3 = (2m-5)((2m)^2+2m(5)+5^2) = (2m-5)(4m^2+10m+25) 2009-01-24 07:48:05 補充： ^ 代表次方 a^2 = a的2次方

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