Question

8) Calcule o valor numérico das expressões:

a) $2a + 3b \: para \: a = - \frac{1}{2} e \: b = \frac{2}{3}$

b) ${x}^{2} + 2x \: para \: x = - 5$

c) $\frac{x + y}{x - y} \: para \: x = 4 \: e \: y = 2$

d) $- b + \sqrt{b {}^{2} } - 4ac \: para \: a = 2 \: b = - 10 \: e \: c = 12$

​passem para a direita se estiverem no celular

Answer 1

Explicação passo-a-passo:

a) $2a+3b$  →  $(a=-\frac{1}{2}$  $e$  $b=\frac{2}{3})$

   $2.(-\frac{1}{2})+3.\frac{2}{3}$

   $-\frac{2}{2}+\frac{6}{3}=-1+2=1$

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b) $x^{2}+2x$  →  $(x=-5)$

   $(-5)^{2}+2.(-5)$

   $(-5).(-5)-10=25-10=15$

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c) $\frac{x+y}{x-y}$  →  $(x=4$  $e$  $y=2)$

   $\frac{4+2}{4-2}=\frac{6}{2}=3$

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d) $-b+\sqrt{b^{2}}-4ac$  →  $(a=2;b=-10;c=12)$

   $-(-10)+\sqrt{(-10)^{2}}-4.2.12$

   $10+\sqrt{100}-96$

   $10+10-96=20-96=-76$