Question

[Phạm Đỗ Bảo Ngọc]

bài 4; tìm x

e, ( x mũ 3 - 4x mũ 2 ) - ( x - 4 ) = 0

f, 2x mũ 3 - 242x = 0

g., x mũ 5 - 9x = 0

Answer 1

[Lê Minh Phương]

đm con chó

Answer 2

[Nguyễn Huy Tú]

e, \(\left(x^3-4x^2\right)-\left(x-4\right)=0\)

\(\Leftrightarrow x^2\left(x-4\right)-\left(x-4\right)=0\Leftrightarrow\left(x^2-1\right)\left(x-4\right)=0\)

\(\Leftrightarrow\left(x+1\right)\left(x-1\right)\left(x-4\right)=0\Leftrightarrow x=\pm1;x=4\)

f, \(2x^3-242x=0\Leftrightarrow2x\left(x^2-121\right)=0\)

\(\Leftrightarrow2x\left(x-11\right)\left(x+11\right)=0\Leftrightarrow x=\pm11;x=0\)

g, \(x^5-9x=0\Leftrightarrow x\left(x^4-9\right)=0\)

\(\Leftrightarrow x\left(x^2-3\right)\left(x^2+3>0\right)=0\Leftrightarrow x=\pm\sqrt{3};x=0\)