Toán Lớp 8: Tìm x biết ( 3x - 5 )^2 - ( 3x + 1 )^2 = 8

Lời giải: (3x-5)^(2)-(3x+1)^2=8 ⇔9x^(2)-30x+25-9x^(2)-6x-1-8=0 ⇔(9x^(2)-9x^2)+(-30x-6x)+(25-1-8)=0 ⇔-36x+16=0 ⇔x=16/36=4/9 Vậy x=4/9

( 3x - 5 )² - ( 3x + 1 )²= 8 ⇔9x² - 30x + 25 - 9x² - 6x -1 = 8 ⇔ -36x= -16 ⇔x= 4/9

Toán Lớp 8: Tìm x biết ( 3x - 5 )^2

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