a/

$\frac{2}{3}$ + $\frac{7}{4}$ : $x$ =$\frac{5}{6}$ ⇔ $\frac{7}{4}$ : $x$ =$\frac{5}{6}$ -$\frac{2}{3}$ ⇔$\frac{7}{4}$ : $x$=$\frac{1}{6}$ ⇔$x$=$\frac{7}{4}$ : $\frac{1}{6}$ ⇔ $x$=$\frac{7}{4}$ .$6$⇔$x$=$\frac{14}{3}$

vậy x=14/3

b/

(x+$\frac{5}{3}$ )(x-$\frac{5}{4}$ )=0 ⇔\(\left[ \begin{array}{l}x+\frac{5}{3}=0\\x-\frac{5}{4}=0\end{array} \right.\) ⇔\(\left[ \begin{array}{l}x=0-\frac{5}{3}\\x=0-\frac{5}{4}\end{array} \right.\) ⇔ \(\left[ \begin{array}{l}x=-\frac{5}{3}\\x=-\frac{5}{4}\end{array} \right.\)

c/

$(x-1,2)^{2}$ =4⇔\(\left[ \begin{array}{l}x-1,2=2\\x-1,2=-2\end{array} \right.\) ⇔\(\left[ \begin{array}{l}x=3,2\\x=-0,8\end{array} \right.\)

d/

$(x+1)^{3}$ =-125⇔x+1=5⇔x=4

Giải thích các bước giải:

a, 7/4:x=5/6-2/3

7/4:x=1/6

x=7/4:1/6

x=21/2

b,x + 5/3=0⇔x=-5/3

x-5/4=0⇔x=5/4

c,(x-1,2)^2=4

(x-1,2)^2=2^2

x-1,2=2

x=5/2

d,(x+1)^3=(-5)^3

x+1=-5

x=-6