Question

 Giúp mk vs ạ

Answer 1

Đề bài yêu cầu là gì vậy bạn?

Answer 2

=>4(5x+3)-120=5(4x-21)

=>20x+12-120=20x-105

=>-108=-105(loại)

Answer 3

Lời giải:

$\frac{5x+3}{15}-2=\frac{4x-21}{12}$

$\frac{5x}{15}+\frac{3}{15}-2=\frac{4x}{12}-\frac{21}{12}$

$\frac{x}{3}+\frac{1}{5}-2=\frac{x}{3}-\frac{7}{4}$

$\frac{x}{3}-\frac{9}{5}=\frac{x}{3}-\frac{7}{4}$

$\Rightarrow \frac{9}{5}=\frac{7}{4}$ (vô lý)

Vậy pt vô nghiệm.

Answer 4

\(\dfrac{5x+3}{15}-2=\dfrac{4x-21}{12}\)

<=> \(\dfrac{4\left(5x+3\right)}{60}-2=\dfrac{5\left(4x-21\right)}{12}\)

<=> \(\dfrac{20x+12}{60}-2=\dfrac{20x-105}{60}\)

<=> \(\dfrac{20x+12}{60}=\dfrac{20x-105}{60}+2\)

<=> \(\dfrac{20x+12}{60}=\dfrac{20x-105+120}{60}\)

<=> \(\dfrac{20x+12}{60}=\dfrac{20x+15}{60}\) (không thỏa mãn)

=> \(\dfrac{5x+3}{15}-2\text{≠}\dfrac{4x-21}{12}\)

#Hy