Question

Giúp em bài 12 vs bài 13 ạ em cảm ơn rất nhiều ạ

Answer 1

Bài 12a. \(541+\left(218-x\right)=735\)

\(\Leftrightarrow218-x=735-541=194\)

\(\Leftrightarrow x=218-194=24\). Vậy x = 24

b. \(96-3.\left(x+1\right)=42\)

\(\Leftrightarrow3.\left(x+1\right)=96-42=54\)

\(\Leftrightarrow x+1=54:3=18\)

\(\Leftrightarrow x=18-1=17\). Vậy x = 17.

c. \(35-\left(2.x-1\right)=28\)

\(\Leftrightarrow2.x-1=35-28=7\)

\(\Leftrightarrow2.x=7+1=8\)

\(\Leftrightarrow x=8:2=4\). Vậy : x = 4.

d. \(580:\left(x-24\right)=329-150.2\)

\(\Leftrightarrow580:\left(x-24\right)=329-300=29\)

\(\Leftrightarrow x-24=580:29=20\)

\(\Leftrightarrow x=20+24=44\). Vậy : x = 44.

e. \(x.\left(x+1\right)-13=17\)

\(\Leftrightarrow x.\left(x+1\right)=17+13=30\)

\(\Leftrightarrow x.x+x=30\)

\(\Leftrightarrow x^2+x-30=0\)

\(\Leftrightarrow x^2+6x-5x-30=0\)

\(\Leftrightarrow\left(x^2+6x\right)-\left(5x+30\right)=0\)

\(\Leftrightarrow x.\left(x+6\right)-5.\left(x+6\right)=0\)

\(\Leftrightarrow\left(x+6\right).\left(x-5\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x+6=0\\x-5=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-6\\x=5\end{matrix}\right.\). Vậy : x = - 6 hoặc x = 5.

f. \(x.x.x-15=12\)

\(\Leftrightarrow x^3-15=12\)

\(\Leftrightarrow x^3=12+15=27\)

\(\Rightarrow x^3=3^3\Rightarrow x=3\). Vậy : x = 3.

Answer 2

Bài 13a. \(4x-2x=18\)

\(\Leftrightarrow\left(4-2\right).x=18\)

\(\Leftrightarrow x=18:\left(4-2\right)=18:2=9\). Vậy : x = 9.

b. \(3.x+2.x-15=40\)

\(\Leftrightarrow\left(3+2\right).x=40+15=55\)

\(\Leftrightarrow x=55:\left(3+2\right)=55:5=11\). Vậy : x = 11.

c và e. \(\left(x+1\right)+\left(x+4\right)+\left(x+7\right)+...+\left(x+28\right)=155\)

\(\Leftrightarrow x+1+x+4+x+7+...+x+28=155\)

\(\Leftrightarrow x+x+x+...+x=155-1-4-7-...-28\) (10 số x).

\(\Leftrightarrow10.x=10\Rightarrow x=1\). Vậy : x = 1

d. \(\left(8.x-1942\right).1947=\left(240-194,2\right).19470\)

\(\Leftrightarrow8.x-1942=\left[\left(240-194,2\right).19470\right]:1947=\dfrac{\left(240-194,2\right).19470}{1947}=\left(240-194,2\right).10\)

\(\Leftrightarrow8.x=\left(240-194,2\right).10+1942=2400-1942+1942=2400\)

\(\Leftrightarrow x=2400:8=300\). Vậy : x = 300.

Ngủ sớm đi nhé em :v