Cho Pt \(\dfrac{x+a}{a-x}+\dfrac{x-a}{a+x}=\dfrac{a\left(3a+1\right)}{a^2-x^2}\)

a) GPT với a = -3

b) Tìm a biết x=\(\dfrac{1}{2}\)

Giải các PT sau:

a) x+1/x = x² + 1/2x²

b) 1/x +2 = ( 1/x+2 ) ( x² +1 )

1. The air in John's area is polluted , so he has breathing problem. ( if / because / because of / make / lead )

2. The soil is posoned because farmers use too many pesticides and herbicides . ( so ) - If farmer ..................

3. Turn off all the lights and you will not pay more money - If you .............. / Unless .........................

4. Be careful or you may have an accident - If ......................... / Unless .............................

5. He can't understand what she has said because he doesn't know English . ( If / so / because of )

6. Many people have stomachache due to the contaminated food ( because / so / if )

7. There is sewage in the lake , so the aquatic animals die . ( because / result / due to / make if )