\(\Leftrightarrow\left(8x+14\right)^2=\left(9x+3\right)^2\)

\(\Leftrightarrow8x+14=9x+3\)

\(\Leftrightarrow x=11\)

I.

D

B

B

C

D

II.

C

D

B

C

A

\(\dfrac{2}{5}+\dfrac{3}{7}=\dfrac{29}{35}\)

sheep

dog

cat

rabbit

cow

C

L

\(\Leftrightarrow4x^2+28x+49=9x^2+36x+36\)

\(\Leftrightarrow5x^2+8x-13=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{13}{5}\end{matrix}\right.\)

anh Thinh sai pk cj :)

a. n có chữ số tận cùng khác 3,8

b. n-3 thuộc Ư(5)= 1,-1,5,-5

n-3=1 => n=4

n-3=-1 => n=2

n-3=5 => n=8

n-3= -5 => n=-2

\(\Leftrightarrow9x^2-54x+81=4x^2+16x+16\)

\(\Leftrightarrow5x^2-80x+65=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=8+\sqrt{51}\\x=8-\sqrt{51}\end{matrix}\right.\)