Toán Lớp 8: Giải phương trình
3-2x=7
3(x-2)-5(x+1)=3
x(x-2)-x(x+1)=15
(3x-1)(2x+5)-(2x-3)(3x+4)=7
(x-1) ²+(x-2) ²=2(x+4) ²-(22x+27)
3x(12x-4)-9x(4x-3)=30
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Toán Lớp 8: Giải phương trình
3-2x=7
3(x-2)-5(x+1)=3
x(x-2)-x(x+1)=15
(3x-1)(2x+5)-(2x-3)(3x+4)=7
(x-1) ²+(x-2) ²=2(x+4) ²-(22x+27)
3x(12x-4)-9x(4x-3)=30
Cần gấp ạ Hứa vote5*
Comments ( 1 )
$b) 3(x – 2)-5(x + 1) = 3$
$⇔ x^2 – 2x – x^2 -1 = 15$
$⇔ -2x -1 = 15$
$⇔ -2x = 16$
$⇔ x = -8$
$d) (3x – 1)(2x + 5)-(2x – 3)(3x + 4) = 7$
$⇔ (6x^2 – 2x + 15x -5) – (6x^2 – 9x + 8x – 12) = 7$
$⇔ 6x^2 + 13x – 5 – 6x^2 + x + 12 = 7$
$⇔ 14x + 7 = 7$
$⇔ 14x = 0$
$⇔ x^2 -2x +1 + x^2 -4x +4= 2x^2 + 16x +32 – 22x – 27$
$⇔2x^2 -6x +5 = 2x^2 – 6x +5$
$⇔(2x^2 -6x +5) – (2x^2 -6x +5) = 0$
$⇔ 0x = 0$
$⇔ x ∈ R$
$ g) 3x(12x-4)-9x(4x-3)=30$
$⇔36x^2 -12x – 36x^2+27x=30$
$⇔15x = 30$
$⇔ x =2$