Question

Pa poate ajuta cineva cu asta raid

Answer 1

Răspuns:

2(1+2+3+...+20)=2·[20·(20+1)]/2=20·21=420

suma lui Gauss

√(21+420)=√441=21

Answer 2

Răspuns: $\red{\boxed{\bf ~21~}}$

Explicație pas cu pas:

$\bf \sqrt{21+2\cdot \big(1+2+3+...+20\big)} =$

$\bf \sqrt{21+2\cdot\big[\big(1+20\big)\cdot 20:2\big]} =$

$\bf \sqrt{21+2\cdot\big(21\cdot 20:2\big)} =$

$\bf \sqrt{21+2\cdot\big(21\cdot 10\big)} =$

$\bf \sqrt{21+2\cdot210} =$

$\bf \sqrt{21+421} = \sqrt{441} = \sqrt{21^{2} } =\red{\boxed{\bf ~21~}}$