đau đầu quá

B

bigbang195

Bài 1 bắt buộc ra hằng số thì mình chịu
bài 2 phân số [TEX]= x+5+\frac{4}{x} \geq 5 + 2\sqrt[]{x.\frac{4}{x}}=5+4=9[/TEX]
dấu [TEX] =[/TEX] xảy ra khi [TEX]x=2[/TEX]
 
K

kuncandy92

[tex]sin^x + cos^4x[/tex]
[tex]=(\frac{1-cos2x}{2})^2+(\frac{1+cos2x}{2})^2[/tex]
[tex]=\frac{1-cos2x +cos^2 2x}{4}+(\frac{1+cos2x +cos^2 2x}{4}[/tex]
[tex]=\frac{2+2cos^2 2x}{4}[/tex]
[tex]=\frac{2(1+cos^2 2x)}{4}[/tex]
[tex]=\frac{1}{2}+\frac{1}{2}(\frac{1+cos4x}{2}[/tex]
[tex]=\frac{1}{2}+\frac{1}{4}+\frac{cos4x}{4}[/tex]
[tex]=\frac{3}{4}+\frac{cos4x}{4}[/tex]
 
Last edited by a moderator:
You must log in or register to reply here.
Top Bottom