Bài 1: 

a. 5x²(-3x³ + 2x - 1)

= -15x⁵ + 10x³ - 5x²

b. \(\left(2x^2-\dfrac{1}{3}xy+y^2\right)\left(-3x^3\right)\)

= \(-6x^5+x^4y-3x^3y^2\)

GHÊ DỊ

Đề ???

Bài 5:

a. (x - 1)(x + 4) - x(x + 2) = 5

<=> x² + 4x - x - 4 - x² - 2x = 5

<=> x² - x² + 4x - x - 2x = 5 + 4

<=> x = 9

b. (x - 2)² - x(x + 5) = 3

<=> x² - 4x + 4 - x² - 5x = 3

<=> x² - x² - 4x - 5x = 3 - 4

<=> -9x = -1

<=> x = \(\dfrac{-1}{-9}=\dfrac{1}{9}\)

Chắc do lỗi ảnh rồi

đề đâu bn nhỉ

\(\dfrac{6}{8}:6=\dfrac{6}{8}.\dfrac{1}{6}=\dfrac{1.1}{8.1}=\dfrac{1}{8}\)

a. 2x² = 10

<=> \(\left(\sqrt{2}x\right)^2-\left(\sqrt{10}\right)^2=0\)

<=> (\(x\sqrt{2}-\sqrt{10}\))(\(x\sqrt{2}+\sqrt{10}\)) = 0

<=> \(\left[{}\begin{matrix}x\sqrt{2}-\sqrt{10}=0\\x\sqrt{2}+\sqrt{10}=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\sqrt{5}\\x=-\sqrt{5}\end{matrix}\right.\)

<=> x = \(\sqrt{5}\)

b. x² = 36

<=> x² - 4² = 0

<=> (x - 4)(x + 4) = 0

<=> \(\left[{}\begin{matrix}x+4=0\\x-4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-4\\x=4\end{matrix}\right.\)

c. \(\sqrt{0,04}-x=3\)

<=> 0,2 - x = 3

<=> -x = 3 - 0,2

<=> -x = 2,8

<=> x = -2,8

d. \(\sqrt{x}\left(x^2-1\right)=0\)                 ĐKXĐ: x \(\ge0\)

<=> \(\sqrt{x}\left(x-1\right)\left(x+1\right)=0\)

<=> \(\left[{}\begin{matrix}\sqrt{x}=0\\x-1=0\\x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x-1\\x=-1\left(loại\right)\end{matrix}\right.\)

e. x² - 2 = 0

<=> x² - \(\left(\sqrt{2}\right)^2\) = 0

<=> (x - \(\sqrt{2}\))(x + \(\sqrt{2}\)) = 0

<=> \(\left[{}\begin{matrix}x-\sqrt{2}=0\\x+\sqrt{2}=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\sqrt{2}\\x=-\sqrt{2}\end{matrix}\right.\)

f. \(\left(x-1\right)^2=\dfrac{4}{9}\)

<=> \(\left(x-1\right)^2-\left(\dfrac{2}{3}\right)^2=0\)

<=> \(\left(x-1-\dfrac{2}{3}\right)\left(x-1+\dfrac{2}{3}\right)=0\)

<=> \(\left[{}\begin{matrix}x-1-\dfrac{2}{3}=0\\x-1+\dfrac{2}{3}=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{3}\\x=\dfrac{1}{3}\end{matrix}\right.\)

(Các câu còn lại tương tự nha, học tốt)

Bn làm rõ ràng ra nha