Question

Calcule o valor numérico das seguintes expressões:
a) 3x + 5, para x = -6.
b) 2a + 7b, para a = - 3 eb= 17.
c) a2 + 3a, para a = -1/2.
d) a? - 2ab + b?, para a =-5 e b = 2.​

Answer 1

Resposta:

a) $-13$

b) $113$

c) $-\frac{5}{4}$

d) $17$

Explicação passo a passo:

a) $3x + 5$

$3\left(-6\right)+5$

$=-18+5$

$=-13$

b) $2a + 7b$

$2\left(-3\right)+7\left(17\right)$

$=-6+7\left(17\right)$

$=-6+119$

$=113$

c) $a^2 + 3a$

$\left(-\frac{1}{2}\right)^2+3\left(-\frac{1}{2}\right)$

$=\left(-\frac{1}{2}\right)^2-3\cdot \frac{1}{2}$

$=\frac{1}{2^2}-\frac{3}{2}$

$=\frac{1}{4}-\frac{3}{2}$

$=\frac{1}{4}-\frac{6}{4}$

$=\frac{1-6}{4}$

$=\frac{-5}{4}$

$=-\frac{5}{4}$

d) $a - 2ab + b$

$\left(-5\right)-2\left(-5\right)\left(2\right)+\left(2\right)$

$=\left(-5\right)-\left(-20\right)+\left(2\right)$

$=\left(-5\right)+20+\left(2\right)$

$=15+\left(2\right)$

$=17$