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10/7(x+0.3)=14

你好!错了0.21,因为1.7x(A十0.3)展开为 1.7x(A十0.3)=1.7xA+0.51用展开式减去1.7xA+0.3 即1.7xA+0.51-(1.7xA+0.3) =1.7xA+0.51-1.7xA-0.3 =0.21 他计算的结果与正确结果相差0.21;希望可以帮到你请采纳谢谢!加油!

7×(x-0.3)+2x=14.5 解:7x-2.1+2x=14.5 7x+2x=14.5+2.1 9x=16.6 x=16.6/9 x=83/45

(x+3)(x-10) =x²-10x+3x-30 =x²-7x-30

(1+7+10+8+x+6+0+3)÷8=535+x=40,x=5.故选B.

x➗0.3-1.7=0.3x 解:x×10╱3=0.3x+1.7 (10╱3-3╱10)x=1.7 (91╱30)x=1.7 x=1.7÷91╱30 x=(17╱10)×(30╱91) x=51╱91

10-0.3(2x-1)=3 +0.4x 解:10-0.6x+0.3=3+0.4x 10.3-0.6x=3+0.4x 10.3=3+0.4x+0.6x 10.3=3+x 10.3-3=x x=7.3

4.2x-2.1=3.7x+37-7.5; 4.2x-3.7x=37-7.5+2.1; 0.5x=31.6; x=63.2。

(1)x: 10 7 =0.4x+12, 7 10 x=0.4x+12, 0.7x-0.4x=12, 0.3x=12, 0.3x÷0.3=12÷0.3, x=40,(2)8×25%+1.3x=10.9,2+1.3x=10.9, 2+1.3x-2=10.9-2, 1.3x=8.9, 1.3x÷1.3=8.9÷1.3, x= 89 13 .

4.2/(x-0.6)=1.4 1.4(x-0.6)=4.2 x-0.6=3 x=3.6 1.2x-(0.6+3.4)=3.2 1.2x-4=3.2 1.2x=7.2 x=6 60%x+14=32.6 0.6x+14=32.6 0.6x=18.6 x=31

E(x)=2*0.2+4*0.3+7*0.4+8*0.1=5.6, D(x)=4*0.2+16*0.3+49*0.4+64*0.1 - 5.6² = 1.04, 所以标准差 s=√[D(x)] = 1.02。

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