Question

Bài 2 Tìm x biết

a) 3 x -5 = 13

b) 4 x - 2 = 3 x +1

c) 5 . ( x - 3) -2 . ( x - 5) =58

d) m x + 5 x = \(^{m^2}\) - 25

Answer 1

Bài 2 Tìm x biết

a) 3x -5 = 13

<=> 3x = 18

<=> x = 6

Vậy x = 6

b) 4x - 2 = 3x + 1

<=> 4x - 3x = 2 + 1

<=> x = 3

Vậy x = 3

c) 5(x - 3) - 2(x - 5) = 58

<=> 5x - 15 - 2x + 10 = 58

<=> 3x - 5 = 58

<=> 3x = 63

<=> x = 21

Vậy x = 21

d) mx + 5x = - 25

<=> mx + 5x + 25 - m² = 0

<=> x(5 + m) + (5 - m)(5 + m) = 0

<=> (5 + m)(x + 5 - m) = 0

<=> \(\left[{}\begin{matrix}5+m=0\\x+5-m=0\end{matrix}\right.\) <=>\(\left[{}\begin{matrix}m=-5\\x+5-m=0\end{matrix}\right.\) => x + 5 - (-5) = 0

<=> x + 10 = 0

<=> x = -10

Vậy x = -10

_{#Không chắc lắm :)}