Question

Encontre o zero das funções:

1) f(x)= -2x+5

2) f(x)= 2x-17

3) f(x)= -3x-15​

Answer 1

1) f(x)= -2x+5

$f(x) = 0\\-2x+5 = 0\\-2x = -5\\x = \frac{-5}{-2}\\x = \frac{5}{2}$

2) f(x)= 2x-17

$f(x) = 0\\2x-17 = 0\\2x = 17\\x = \frac{17}{2}$

3) f(x)= -3x-15​

$f(x) = 0\\-3x-15 = 0\\-3x = 15\\x = \frac{15}{-3}\\x = -5$

Answer 2

Explicação passo-a-passo:

Questão 1:

$f(x) = - 2x = - 5 \\ - 2x = - 5 \: <strong> </strong><strong>*</strong><strong>( - 1)</strong><strong>\</strong><strong>:</strong> Como\: o\:valor\:de\:X \:é\:negativo,\\ vamos\:multiplicar \:por \:-1 \\ 2x = 5 \\ x = \frac{5}{ 2}$

Prova:

$Substituir\:o\:X\:por\:\frac{5}{ 2}$

$f(</strong><strong>\frac{5}{2}</strong><strong>) = - 2</strong><strong>(</strong><strong>\frac{5}{ 2}</strong><strong> </strong><strong>)</strong><strong> </strong><strong>+</strong><strong> </strong><strong>5</strong><strong>\</strong><strong>:</strong><strong> </strong><strong> </strong><strong>\\ </strong><strong>-</strong><strong>5</strong><strong> </strong><strong>+</strong><strong> </strong><strong>5 </strong><strong>=</strong><strong> </strong><strong>0</strong><strong> </strong><strong>$

Questão 2:

$f(x) = 2x = </strong><strong>1</strong><strong>7</strong><strong> </strong><strong>\</strong><strong>\</strong><strong>x = \frac{</strong><strong>1</strong><strong>7</strong><strong>}{ 2}$

Prova:

$Substituir\:o\:X\:por\:\frac{</strong><strong>1</strong><strong>7</strong><strong>}{ </strong><strong>2</strong><strong>}$

$f(\frac{</strong><strong>1</strong><strong>7</strong><strong>}{2}) = 2(\frac{</strong><strong>1</strong><strong>7</strong><strong>}{ 2} ) </strong><strong>-</strong><strong> </strong><strong>1</strong><strong>7</strong><strong> \\ </strong><strong>1</strong><strong>7</strong><strong> </strong><strong>-</strong><strong> </strong><strong>1</strong><strong>7</strong><strong> = 0$

Questão 3:

$f(x) = - </strong><strong>3</strong><strong>x = </strong><strong>1</strong><strong>5 \\ - </strong><strong>3</strong><strong>x = </strong><strong>1</strong><strong>5 \: *( - 1)\: Como\: o\:valor\:de\:X \:é\:negativo,\\ vamos\:multiplicar \:por \:-1 \\ </strong><strong>3</strong><strong>x = </strong><strong>-</strong><strong> </strong><strong>1</strong><strong>5 \\ x = \frac{</strong><strong>-</strong><strong> </strong><strong>1</strong><strong>5}{ </strong><strong>3</strong><strong>}</strong><strong> \\ x = </strong><strong>-</strong><strong> </strong><strong>5</strong><strong>$

Prova:

$Substituir\:o\:X\:por\:</strong><strong>-</strong><strong> </strong><strong>5</strong><strong>$

$f(</strong><strong>5</strong><strong>) = - </strong><strong>3</strong><strong>(</strong><strong>-</strong><strong>5</strong><strong> ) </strong><strong>-</strong><strong> </strong><strong>1</strong><strong>5\: \\ </strong><strong>1</strong><strong>5 </strong><strong>-</strong><strong> </strong><strong>1</strong><strong>5 = 0$