標題:
Equations
發問:
1. {xy=108 {x^2+y^2=225 2.A factory produces 40 T-shirts in N hours.If the factory produces 2 more T-shirt each hour,it will take 1hour less to produce 40 T-shirts.Find N.
最佳解答:
1. xy = 108 ?????? (1)x2＋y2＝225 ?????? (2)(2)＋2*(1) get x2＋2xy＋y2＝441 ==> x＋y＝21 or -21 ?? (3)(2)－2*(1) getx2－2xy＋y2＝9==> x－y＝3 or -3 ??? (4)Solve (3), (4) get(x, y) = (12, 9), (9, 12), (-12, -9) or (-9, -12) 2. Each hour the factory produces 40/N, so,40/N＋2＝40/(N－1)==> 40(N－1)＋2N(N－1)＝40N==> 20N－20＋N2－N＝20N==> N2－N－20＝0==> (N－5)(N＋4)＝0==> N＝5 or -4(rej)
其他解答:
Equations
發問:
1. {xy=108 {x^2+y^2=225 2.A factory produces 40 T-shirts in N hours.If the factory produces 2 more T-shirt each hour,it will take 1hour less to produce 40 T-shirts.Find N.
最佳解答:
1. xy = 108 ?????? (1)x2＋y2＝225 ?????? (2)(2)＋2*(1) get x2＋2xy＋y2＝441 ==> x＋y＝21 or -21 ?? (3)(2)－2*(1) getx2－2xy＋y2＝9==> x－y＝3 or -3 ??? (4)Solve (3), (4) get(x, y) = (12, 9), (9, 12), (-12, -9) or (-9, -12) 2. Each hour the factory produces 40/N, so,40/N＋2＝40/(N－1)==> 40(N－1)＋2N(N－1)＝40N==> 20N－20＋N2－N＝20N==> N2－N－20＝0==> (N－5)(N＋4)＝0==> N＝5 or -4(rej)
其他解答:
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