Question

Calculează 298-295+292-289+.....10-7+4-1=

Answer 1

 

$\displaystyle\bf\\298-295+292-289+...+10-7+4-1=?\\\\\text{\bf Aflam numarul de numere (n) din sir, facand abstractie de semn.}\\\\n=\frac{298-1}{3}+1=\frac{297}{3}+1=99+1=100~de~numere\\\\\text{\bf Grupam numerele in grupe de cate 2 numere.}\\\\\text{\bf Vom obtie: }~ \frac{100~de~numere}{2}=50~de~grupe\\\\ (298-295)+(292-289)+...+(10-7)+(4-1)=\\\\=\underbrace{3+3+...+3+3}_{50~de~treiuri}=50\times3=\boxed{\bf150}$