Question

O número de diagonais de um polígono de 18 lados é igual a

a) 20

b) 44

c) 104

d) 135​

Answer 1

Oie!

❒ Fórmula:

$\green{ \boxed{ \boxed{ \boxed{D=n(n-3)÷2}}}}$

n ©==> Número de lados.

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❒ Aplicando a fórmula:

$\green{ \boxed{ \boxed{ \boxed{</strong><strong>D</strong><strong>=</strong><strong> </strong><strong>1</strong><strong>8</strong><strong>(</strong><strong>1</strong><strong>8</strong><strong>-</strong><strong>3</strong><strong>)</strong><strong> </strong><strong>÷</strong><strong> </strong><strong>2</strong><strong>}}}}$ ©==>

$\boxed{ \boxed{ \boxed{</strong><strong>D</strong><strong> </strong><strong>=</strong><strong> </strong><strong>1</strong><strong>8</strong><strong> </strong><strong>(</strong><strong>1</strong><strong>5</strong><strong>)</strong><strong> </strong><strong>÷</strong><strong>2</strong><strong>}}}$ ©==>

✎ Multiplique 18 por 15:

$\: \: \: 18 \\ \times 15 \\ = = = \\ + 90 \\ 180 \\ = = = \\ \red{ 270}$

✎ Agora Continue:

$\boxed{ \boxed{ \boxed{</strong><strong>D</strong><strong> </strong><strong>=</strong><strong> </strong><strong>2</strong><strong>7</strong><strong>0</strong><strong> </strong><strong>÷</strong><strong> </strong><strong>2</strong><strong>}}}$ ©==>

$\boxed{ \boxed{ \boxed{135}}} </strong></p><p></p><h2>→</h2><p><strong> </strong><strong>\red{ \boxed{ \boxed{ \boxed{</strong><strong>♠</strong><strong>♣</strong><strong>♪</strong><strong>★</strong><strong>alternativa \: d}}}}$

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Bons estudos!

Especialista Cebolinha.

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