Question

me ajudem por favor.

Answer 1

Boa tarde!

a)
$y=\dfrac{x(x+1)}{2}\\y=\dfrac{1\,000(1\,000+1)}{2}\\y=\dfrac{1\,000\cdot 1\,001}{2}=500\cdot 1\,001\\y=500\,500$

b)
$66=\dfrac{x(x+1)}{2}\\x^2+x=132\\x^2+x-132=0\\\Delta=1^2-4(1)(-132)\\\Delta=1+528\\\Delta=529\\x=\dfrac{-(1)\pm\sqrt{529}}{2(1)}\\x=\dfrac{-1\pm 23}{2}\\x'=\dfrac{-1+23}{2}=11\\x''=\dfrac{-1-23}{2}=-12$

Então, 11 é o número positivo.

Espero ter ajudado!