(12x-10)/21-(2-x)/15=(8x-9)/24-(7x -9)/20 求x 急
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(12x-10)/21-(2-x)/15=(8x-9)/24-(7x -9)/20 求x 急
![(12x-10)/21-(2-x)/15=(8x-9)/24-(7x -9)/20 求x 急](/uploads/image/z/16543141-61-1.jpg?t=%EF%BC%8812x-10%EF%BC%89%2F21-%EF%BC%882-x%EF%BC%89%2F15%EF%BC%9D%EF%BC%888x-9%29%2F24-%287x+-9%29%2F20+%E6%B1%82x+%E6%80%A5)
(12x-10)/21-(2-x)/15=(8x-9)/24-(7x -9)/20
∵21=3*7,15=3*5,24=2³*3,20=2²*5
∴ 21,15,24,20的最小公倍数为2³*3*5*7
∴等式两边同时乘以这个数
得到40(12x-10)-56(2-x)=35(9x-9)-42(7x-9)
即 (40*12+56-35*9+42*7)x=40*10+56*2-35*9+42*9
550x=575
∴ x=575/550=23/22
恭喜楼主做对了.
∵21=3*7,15=3*5,24=2³*3,20=2²*5
∴ 21,15,24,20的最小公倍数为2³*3*5*7
∴等式两边同时乘以这个数
得到40(12x-10)-56(2-x)=35(9x-9)-42(7x-9)
即 (40*12+56-35*9+42*7)x=40*10+56*2-35*9+42*9
550x=575
∴ x=575/550=23/22
恭喜楼主做对了.
1x+2x+3x+4x+5x+6x+7x+8x+9x+10x+11x+12x+13x+14x+15x=550
(12x-10)/21+(7x-9)/20=(2-x)/15+(8x-9)/12
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