Tìm x , biết
( làm đầy đủ nhé )
a) (2x +3)(x – 4) + (x – 5)(x – 2) = (3x – 5)(x – 4)
b) (8x – 3)(3x +2 ) – ( 4x + 7 )(x + 4) = ( 4x + 1 ) ( 5x – 1 )
c) 2x^2 + 3(x – 1)(x + 1 ) = 5x(x + 1 )
d) ( 8 – 5x) ( x + 2 ) + 4(x – 2)(x + 1 ) + ( x – 2 ) ( x + 2 ) = 0
#Làm sai = báo cáo
Đáp án:
Giải thích các bước giải:
`a) (2x +3)(x – 4) + (x – 5)(x – 2) = (3x – 5)(x – 4)`
`⇔ 2x² – 8x + 3x – 12 + x² – 2x – 5x + 10 = 3x² – 12x – 5x + 20`
`⇔ 2x² + x² – 3x² – 8x + 3x – 2x – 5x + 12x + 5x = 20 + 12 – 10`
`⇔ 5x = 22`
`⇔ x = 225225`
`b) (8x – 3)(3x +2 ) – ( 4x + 7 )(x + 4) = ( 4x + 1 ) ( 5x – 1 )`
`⇔ 24x² + 16x – 9x – 6 – 4x² – 16x – 7x – 28 = 20x² – 4x + 5x – 1`
`⇔ 24x² – 4x² – 20x² + 16 x – 9x – 16x – 7x + 4x – 5x = 6 + 28 – 1`
`⇔ -17x = 33`
`⇔ x = −3317−3317`
`c) 2x^2 + 3(x – 1)(x + 1 ) = 5x(x + 1 )`
`⇔ 2x² + 3( x² – 1 ) = 5x² + 5x`
`⇔ 2x² + 3x² – 3 = 5x² + 5x`
`⇔ 2x² + 3x² – 5x² – 5x = 3`
`⇔ -5x = 3`
`⇔ x = −35−35`
`d) ( 8 – 5x) ( x + 2 ) +4 (x – 2)(x + 1 ) + ( x – 2 ) ( x + 2 ) = 0`
`⇔ 8x + 16 – 5x² – 10x + 4 ( x² + x – 2x – 2 ) + x² – 4 = 0`
`⇔ 8x + 16 – 5x² – 10x + 4x² + 4x – 8x – 8 + x² – 4 = 0`
`⇔ -5x² + 4x² + x² + 8x – 10x + 4x – 8x = 4 + 8 – 16`
`⇔ -6x = -4`
`⇔ x = −4−6−4−6`
`⇔ x = 2323`
Xin hay nhất !
a) (2x +3)(x – 4) + (x – 5)(x – 2) = (3x – 5)(x – 4)
⇔ 2x² – 8x + 3x – 12 + x² – 2x – 5x + 10 = 3x² – 12x – 5x + 20
⇔ 2x² + x² – 3x² – 8x + 3x – 2x – 5x + 12x + 5x = 20 + 12 – 10
⇔ 5x = 22
⇔ x = $\frac{22}{5}$
b) (8x – 3)(3x +2 ) – ( 4x + 7 )(x + 4) = ( 4x + 1 ) ( 5x – 1 )
⇔ 24x² + 16x – 9x – 6 – 4x² – 16x – 7x – 28 = 20x² – 4x + 5x – 1
⇔ 24x² – 4x² – 20x² + 16 x – 9x – 16x – 7x + 4x – 5x = 6 + 28 – 1
⇔ -17x = 33
⇔ x = $\frac{-33}{17}$
c) 2x^2 + 3(x – 1)(x + 1 ) = 5x(x + 1 )
⇔ 2x² + 3( x² – 1 ) = 5x² + 5x
⇔ 2x² + 3x² – 3 = 5x² + 5x
⇔ 2x² + 3x² – 5x² – 5x = 3
⇔ -5x = 3
⇔ x = $\frac{-3}{5}$
d) ( 8 – 5x) ( x + 2 ) + 4(x – 2)(x + 1 ) + ( x – 2 ) ( x + 2 ) = 0
⇔ 8x + 16 – 5x² – 10x + 4 ( x² + x – 2x – 2 ) + x² – 4 = 0
⇔ 8x + 16 – 5x² – 10x + 4x² + 4x – 8x – 8 + x² – 4 = 0
⇔ -5x² + 4x² + x² + 8x – 10x + 4x – 8x = 4 + 8 – 16
⇔ -6x = -4
⇔ x = $\frac{-4}{-6}$
⇔ x = $\frac{2}{3}$
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