Their clothes used to be washed without detergent

Those books must be returned to the library soon

The cheque must be signed by the manager

English had to be spoken in the club

Do the flowers have to be watered every 2 days?

Tickets won't have to be bought so early

their clothes used to be washed without detergent

the books must be returned to the library soon

\(\left\{{}\begin{matrix}x=5-y\\y\left(5-y\right)=4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=1\\y=4\end{matrix}\right.\\\left\{{}\begin{matrix}x=4\\y=1\end{matrix}\right.\end{matrix}\right.\)

All the paper was blown away by the wind.

Dozens of trees were destroyed by the storm.

Nancy a pay increase was offered (by them)

1: Thay x=16 vào A, ta được:

\(A=\dfrac{4-1}{4+3}=\dfrac{3}{7}\)

2: \(P=A:B\)

\(=\dfrac{\sqrt{x}-1}{\sqrt{x}+3}:\dfrac{x-3\sqrt{x}-x-6\sqrt{x}-9+x+11\sqrt{x}+6}{x-9}\)

\(=\dfrac{\sqrt{x}-1}{1}\cdot\dfrac{\sqrt{x}-3}{x+2\sqrt{x}-3}=\dfrac{\sqrt{x}-3}{\sqrt{x}+3}\)

5:

a: AD/CD=BA/BC=3/5

b: ΔBAD đồng dạng vói ΔBHD

ΔCHD đồng dạng với ΔCAB

c: ΔCHD đồng dạng với ΔCAB

=>HD/AB=CD/CB

=>HD*CB=AB*CD

a) Thay m = -2 vào (P) ta có:

\(y=\left(-2-3\right)x+\left(-2\right).\\ \Leftrightarrow y=-5x-2.\)

i) + \(y=-5x-2.\)

\(Cho\) \(x=0.\Rightarrow y=-2.\)

\(Cho\) \(y=0.\Rightarrow x=\dfrac{-2}{5}.\)

+ \(y=2x^2.\)