b: \(\sqrt{8^2+6^2}-\sqrt{16}+\dfrac{1}{2}\sqrt{\dfrac{4}{25}}\)

\(=10-4+\dfrac{1}{2}\cdot\dfrac{2}{5}=6+\dfrac{1}{5}=\dfrac{31}{5}\)

4:

a: căn x-1=3

=>căn x=4

=>x=16

b: căn x-3=2

=>căn x=5

=>x=25

c: 5/12*căn x-1/6=1/3

=>5/12*căn x=1/2

=>căn x=1/2:5/12=1/2*12/5=12/10=6/5

=>x=36/25

d: căn x-1-3=0

=>căn x-1=3

=>x-1=9

=>x=10

e: =>căn x+1=1

=>x+1=1

=>x=0

f: =>|3/5*căn x-1/20|=1/5+3/4=19/20

=>3/5*căn x-1/20=-19/20 hoặc 3/5*căn x-1/20=19/20

=>3/5*căn x=1

=>căn x=5/3

=>x=25/9

a: \(\widehat{B}+\widehat{C}=90^0\)

c: Góc kề bù với C bằng tổng của góc A cộng góc B

bài đâu bạn

Dear My friend

I live in Ha Noi. It’s the capital of Vietnam. I’ve been living here for 5 years and I believe it’s the place that suits me most. The city has great culture to explore and offers good opportunities of career and education.People who live here is very friendly and helpful. But the crowded congested traffic is a real issue here, it’s an ideal place to meet people from over the world. It’s always changing so you’ll hardly get bored at this sleepless city.

Best regards,

(Your name)

Bài 4: 

a: \(=42-44=-2\)

b: =73,5-50=23,5

98 và 12

... bn check lại đề chỗ chất D nhé, tính bị sai á

mình nghĩ "thu được 12,8 gam khí SO₂" hợp lý hơn :)

\(A=\dfrac{3}{2}-tana\cdot cos^2a\)

\(=\dfrac{3}{2}-\dfrac{sina}{cosa}\cdot cos^2a\)

\(=\dfrac{3}{2}-sina\cdot cosa\)

\(=\dfrac{3}{2}-\dfrac{1}{2}sin2a\)
\(0^0< a< 90^0\)

=>\(0< =2a< =180^0\)

=>\(sin2a\in\left[-1;1\right]\)

\(-1< =sin2a< =1\)

=>\(\dfrac{1}{2}>=-\dfrac{1}{2}sin2a>=-\dfrac{1}{2}\)

=>\(\dfrac{7}{2}>=-\dfrac{1}{2}sin2a+3>=\dfrac{5}{2}\)

=>\(\dfrac{5}{2}< =y< =\dfrac{7}{2}\)

\(y_{min}=\dfrac{5}{2}\) khi sin2a=1

=>\(2a=\dfrac{\Omega}{2}+k2\Omega\)

=>\(a=\dfrac{\Omega}{4}+k\Omega\)

mà 0<a<90

nên a=45