Karate is my favorite sport
My favourite sport is karate, which is one of the Oriental martial arts. Karate is a popular sport in the world because it improves self-confidence and self-discipline, memory and attention. Besides, karate teaches us self-defence, respect, self-control and patience.
I started practising karate when I was eight. Since that time I have been training twice a week in our local sports centre. The lessons are physically hard but I enjoy them. Our sensei teaches us patiently and inspires us to become better people. I have already participated in a few competitions.
I am glad that I chose karate because it gives me so much: I have become more patient and physically stronger.
Объяснение:
S=(2a1+(n-1)d)/2*n
80=(2a1+dn-d)/2 *n
(2a1+dn-d)n=160
(6+2n-2)n=160
(2n+4)n=160
(n+2)n=80
n^2+2n-80=0
n=-10; n=8
n>0 => n=8
ответ: 8