Question

URGEEEEEEEEEEEEENT!
EXERCITIUL 30


VA ROG FRUMOS, AZI DAU TEST!!!

Answer 1

$\it b=2(-1+2-3+4-\ ...\ -199+200)=\\ \\ =2\cdot[(-1+2)+(-3+4)+\ ...\ +(-199+200)]=\\ \\ =2\cdot(\underbrace{1+1+1+\ ...\ +1}_{de\ 100\ ori})=2\cdot100=200\\ \\ a=[(-1+2)+(-3+4)+\ ...\ +(-399+400)]=\\ \\ =\underbrace{1+1+1+\ ...\ +1}_{de\ 200\ ori}=200$

Deci, a = b.