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2x%0.8*2=25.4解方程

2x-0.8*2=25.4 2x-1.6=25.4 2x=25.4+1.6 2x=27 x=13.5

解:2x=25.4+1.6 2x=27 x=27÷2 x=13.5

(1)2x+4×0.8=24.2, 2x+3.2=24.2, 2x+3.2-3.2=24.2-3.2, 2x=21, x=10.5;(2)29:12=x:45, 12x=29×45, 12x=845, 12x×2=845×2, x=1645;

2x-0.8*2=25.4 2x=25.4+1.6 2x=27 x=13.5 3*8+15x=46.5 15x=46.5-24 15x=22.5 x=1.5 x-8*0.9=2.4 x=2.4+7.2 x=9.6

(1)∵x2-2x=0,∴x(x-2)=0,即x=0或x-2=0,解得:x1=0,x2=2;(2)∵(x+2)2-25=0,∴(x+2)2=25,∴x+2=±5,解得:x1=3,x2=-7;(3)∵(x-1)(x-3)=8,∴x2-4x-5=0,∴(x-5)(x+1)=0,即x-5=0或x+1=0,解得:x1=5,x2=-1;(4)∵2x2-7x+3...

解:x2-6x-7=0 x2-6x=7 x2-6x+9=7+9 (x-3)2=16 ∴x-3=4或x-3=-4, 所以x=7或x=-1

设x 2 -1=t,原方程可化为t 2 -5t+4=0,即(t-1)(t-4)=0,解得,t=1或t=4.当t=1时,x 2 -1=1,解得,x=± 2 ;当t=4时,x 2 -1=4,解得x= ± 5 所以原方程的解是:x 1 = 2 ,x 2 =- 2 ,x 3 = 5 ,x 4 =- 5 .

2x=0.8+0.5*2 2x=1.8 x=0.9

(1)2x+0.82﹦8.2 2x+0.82+0.82﹦8.2+0.82 2x=9.02 2x÷2=9.02÷2 x=4.51;(2)3+0.5x﹦7 3+0.5x-3﹦7-3 0.5x=4 0.5x÷0.5=4÷0.5 x=8;(3)7.8÷x﹦2.6 7.8÷x×x﹦2.6×x 7.8=2.6x 7.8÷2.6=2.6x÷2.6 x=3;(4)80x÷4﹦12 80x÷4×4﹦12×4 80x﹦48 80x...

2x+4=2.8 2x=-1.2 x=-0.6

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