\(\sqrt{x^{ }2-6x+9}=4-x\)
\(\sqrt{\left(x-3\right)^{ }2}=4-x\)
x-3=4-x
x+x=4+3
2x=7
x=\(\dfrac{7}{2}\)

43, Did you come
45,are cleaned
48,took
50, haven't met
55, eating
 

cot B = \(\dfrac{5}{13}=>tanB=\dfrac{13}{5}\)
AC=AB.tanB
AC= 15.\(\dfrac{13}{5}\)
AC= 39cm
BC²=AB²+AC²
BC²=225+1521=1746
BC=3 \(\sqrt{194}\)

1,Uyen started learn 2 weeks ago
4,She started take the children in this remote village  five months ago
5, It took Anna three days to vist Vietnam
6. My son spent three years studying in this college. 
7. It takes me two hours to do my homework every day.
 

2, My great grandma used to take me to the park everyday
3, She used to write to him 
4, I used to go fishing with my Dad when I was young
5, Lisa used to talk to Peter
6, Andy used to get up last year
7, Ther street used to have many old houses
8, Ther used to be a post office near my house 
9,my sister used to buy me a lot of candy
10, Tuan used to play soccer a lot when he was in high shool

4x²-4x - 9
= 4x² - 4x +1 - 10
= (2x -1)² - 10 lớn hơn hoặc bằng -10
GTNN của 4x²-4x - 9 xảy ra khi (2x -1)² = 0
                                                     2x-1 = 0
                                                     2x = 1
                                                       x=\(\dfrac{1}{2}\)

AC=AB.tg B
AC= 30.\(\dfrac{8}{15}\)
AC= 16cm
BC²=AB²+AC²
BC² = 900+256=1156
BC=34cm

13, I wish I had gotten time to listen to you.
15, Mike doesn't plays tennis as well as Bob

a)
4/9 < 5/10 mà 5/10 =1/2
=> 4/9<1/2