bài 1: tìm x, biết: a) 3(5x -1) – x( x – 2) + x2 – 13x = 7 b) 4×2 – 2x + 3 – 4x(x – 5) = 7x-3 giúp mk vs 22/08/2021 Bởi Valentina bài 1: tìm x, biết: a) 3(5x -1) – x( x – 2) + x2 – 13x = 7 b) 4×2 – 2x + 3 – 4x(x – 5) = 7x-3 giúp mk vs
`a) 3(5x -1) – x( x – 2) + x^2 – 13x = 7` `⇔15x-3-x^2+2x+x^2-13x=7` `⇔(-x^2+x^2)+(15x+2x-13x)=7+3` `⇔4x=10` `⇔x=10:4` `⇔x=5/2` Vậy `x=5/2.` `b) 4x^2 – 2x + 3 – 4x(x – 5) = 7x-3` `⇔4x^2-2x+3-4x^2+20x -7x +3=0` `⇔(4x^2-4x^2)-(2x+7x-20x)=0-3-3` `⇔-(-11x)=-6` `⇔-11x=6` `⇔x=6:(-11)` `⇔x=-6/11.` Vậy `x=-6/11.` Bình luận
Đáp án: Giải thích các bước giải: a) $3(5x-1) – x(x-2) + x² – 13x = 7$ $15x – 3 – x² + 2x + x² – 13x = 7$ $4x = 10$ $x = \dfrac{5}{2}$ b) $4x² – 2x + 3 – 4x(x-5) = 7x – 3$ $4x² – 2x + 3 – 4x² + 20x – 7x = -3$ $11x = -6$ $x = \dfrac{-6}{11}$ Bình luận
`a) 3(5x -1) – x( x – 2) + x^2 – 13x = 7`
`⇔15x-3-x^2+2x+x^2-13x=7`
`⇔(-x^2+x^2)+(15x+2x-13x)=7+3`
`⇔4x=10`
`⇔x=10:4`
`⇔x=5/2`
Vậy `x=5/2.`
`b) 4x^2 – 2x + 3 – 4x(x – 5) = 7x-3`
`⇔4x^2-2x+3-4x^2+20x -7x +3=0`
`⇔(4x^2-4x^2)-(2x+7x-20x)=0-3-3`
`⇔-(-11x)=-6`
`⇔-11x=6`
`⇔x=6:(-11)`
`⇔x=-6/11.`
Vậy `x=-6/11.`
Đáp án:
Giải thích các bước giải:
a)
$3(5x-1) – x(x-2) + x² – 13x = 7$
$15x – 3 – x² + 2x + x² – 13x = 7$
$4x = 10$
$x = \dfrac{5}{2}$
b)
$4x² – 2x + 3 – 4x(x-5) = 7x – 3$
$4x² – 2x + 3 – 4x² + 20x – 7x = -3$
$11x = -6$
$x = \dfrac{-6}{11}$