\(800\) \(+\) \(x\) \(-\) \(90\)\(=\) \(980\)

\(\text{800 + x = 980 + 90}\)

\(\text{800 + x = 1017}\)

\(\text{x = 1017 - 800}\)

\(\text{x = 270}\)

 \(x-22=16+14\)

\(\Leftrightarrow\)\(x-22=30\)

\(\Leftrightarrow\)\(x=30+22\)

\(\Leftrightarrow\)\(x=52\)

\(\text{Vậy x = 52}\)

\(\text{1 + 1 = 2}\)

\(\dfrac{8x^2-2}{4x^2y}-\dfrac{4x^2-2}{4x^2y}=\dfrac{2\left(2x-1\right)\left(2x+1\right)}{4x^2y}-\dfrac{4x^2-2}{4x^2y}=\dfrac{2\left(2x-1\right)\left(2x+1\right)}{2x^2y}-\dfrac{2\left(2x^2-1\right)}{4x^2y}\)

\(=\dfrac{\left(2x-1\right)\left(2x+1\right)}{2x^2y}-\dfrac{2x^2-1}{2^2y}=\dfrac{\left(2x-1\right)\left(2x+1\right)-\left(2x^2-1\right)}{2x^2y}=\dfrac{2x^2}{2x^2y^{ }}\)

\(=\dfrac{1}{y}\)

Có cái nào đúng đâu trời ơi

\(x^3+9x^2+27x+27\) 

\(=\left(x+3\right)^3\) \(\left(A\right)\)

\(\text{Với x = 7, ta thay vào biểu thức (A), ta có:}\)

\(\left(x+3\right)^3=\left(7+3\right)^3=10^3=1000\)

\(\Rightarrow\text{tại x = 7 thì có biểu thức trên có giá trị bằng 1000}\)

\(1+1=2\)

Bài 3:

A. 10, 07

Bài 4:

\(1\dfrac{5}{10}=1,5\)

\(3\dfrac{32}{1000}=3,032\)

\(\dfrac{1}{3}x-\dfrac{3}{2}x=\dfrac{1}{5}\)

\(\dfrac{-7}{6}x=\dfrac{1}{5}\)

\(x=\dfrac{1}{5}.\left(\dfrac{-6}{7}\right)\)

\(x=\dfrac{-6}{35}\)

a) \(\dfrac{18}{24}+\dfrac{15}{-10}=\dfrac{9}{12}+\dfrac{-5}{2}=\dfrac{9}{12}+\dfrac{-30}{12}=\dfrac{-21}{12}=\dfrac{-9}{4}\)

b) \(\dfrac{-3}{27}+\dfrac{56}{28}=\dfrac{-1}{9}+2=\dfrac{9\times2-1}{9}=\dfrac{17}{9}\)