\(\dfrac{1}{2}+\dfrac{1}{4}\div\dfrac{1}{4}=\dfrac{1}{2}+1=\dfrac{1}{2}+\dfrac{2}{2}=\dfrac{3}{2}\)

\(\left(3x+9\right)^2=\overline{a25}\)

Do \(\overline{a25}\) có tận cùng = 5 nên số đó sẽ là bình phương của 1 số có tận cùng là 5. Do đó a ϵ {2; 6}

Do đó khi \(\overline{a25}=225=15^2=\left(-15\right)^2\) 

           khi \(\overline{a25}=625=25^2=\left(-25\right)^2\)

TH1:

\(3x+9=15\)

\(3x=15-9\)

\(3x=6\)

\(x=6\div3\)

\(x=2\)

TH2:

\(3x+9=-15\)

\(3x=-15-9\)

\(3x=-24\)

\(x=\left(-24\right)\div3\)

\(x=-8\)

TH3:

\(3x+9=25\)

\(3x=25-9\)

\(3x=16\)

\(x=16\div3\)

\(x=\dfrac{16}{3}\)

TH4:

\(3x+9=-25\)

\(3x=-25-9\)

\(3x=-34\)

\(x=\left(-34\right)\div3\)

\(x=\dfrac{-34}{3}\)

Vậy x ϵ {\(\dfrac{-34}{3};\dfrac{16}{3};-8;2\)}

X x (1 + 2 + 3 + 4) = 2130

X x 10 = 2130

X = 2130 : 10

X = 213

Vậy X = 213

a) off

b) at

c) in

d) out of 

e) under

f) by

g) without

h) on

i) to

j) for

She is hard-working, so she doesn't mind doing homework.

My family has decided to visit Da Lat in the summer.

4^x = 64

4^x = 4³

⇒ x = 3

Vậy x = 3

1; 5; 9; 13; 17; ...

Mỗi số hạng cách nhau 4 đơn vị.

Số hạng thứ 50 của dãy là:

1 + 4 x (50 - 1) = 197

Đáp số: 197

\(\dfrac{2}{3}+\dfrac{2}{5}=\dfrac{10}{15}+\dfrac{6}{15}=\dfrac{16}{15}\)

My best friend is Alan. Alan is a tall guy with short brown hair and glasses. He is friendly, intelligent and really talented. He knows a lot about animations and is able to create many awsome art works. We usually study and hang out together and he taught me pretty much! Alan is such a good friend and you would definitely like him.