a) (a+b).(a+b)=(a+b)²

a) (a-b).(a-b)=(a-b)²

(2x + 1) + (2x + 2) +...+ (2x + 10) = 650

=> 2x+1+2x+2+...+2x+10=650

=> (2x+2x+...+2x)+(1+2+3+...+10)=650

=> 10.2x+55=650

=> 20x=650-55

=> 20x=595

=> x=595:20

=> x=29,75

1. I don't watch news because it is boring

2. She is seeing a movie at cinema but the film is terrifying

3. The programme is boring and the MC is bored

4. I have a lot of homework tonight so I can't watch Eight Feet Below

5. Although BBC The Coast a famous TV series.I have never watched it

1+2+3+...+x=\(\frac{x\left(x+1\right)}{2}\)

-\(\frac{x\left(x+1\right)}{2}\)=-210

\(\frac{x\left(x+1\right)}{2}\)=210

x(x+1)=420

=>x=20