✔ 最佳答案
(0.7+x)^2=(1.3-2x)^2
0.49+1.4x+x^2=1.69-5.2x+4x^2
3x^2-6.6x+1.2=0
x^2-2.2x+6.4=0
(x-1.2)(x-2)=0
x=1.2 或 x=2
2006-12-31 17:57:21 補充:
應該係咁樣先岩, 岩岩寫錯左少少野.(0.7 x)^2=(1.3-2x)^20.49 1.4x x^2=1.69-5.2x 4x^23x^2-6.6x 1.2=0x^2-2.2x 6.4=0(x-0.2)(x-2)=0x=0.2 或 x=2