Question

calcule o valor numérico da expressão3x.x+5x-6 sendo
a)x=2
b)x=-2
c)x=3

Answer 1

a)3.2.2+5.2-6=
12+10-6
16
b)3.(-2).(-2)+5.(-2)-6=
-6.(-2)-10-6=
12-10-6=
-4
c)3.3.3+5.3-6=
27+15-6
36

Answer 2

$a) \: 3 {x}^{2} + 5x - 6 = \\ 3 \times {(2)}^{2} + 5 \times (2) - 6 = \\ 3 \times 4 + 10 - 6 = \\ 12 + 10 - 6 = 22 - 6 = 16$
$b) \: 3 {x}^{2} + 5x - 6 = \\ 3 \times {( - 2)}^{2} + 5 \times ( - 2) - 6 = \\ 3 \times 4 - 10 - 6 = 12 - 10 - 6 = 2 - 6 = \\ - 4$
$c) \: 3 {x}^{2} + 5x - 6 = 3 \times {(3)}^{2} + 5 \times 3 - 6 = \\ 3 \times 9 + 15 - 6 = 27 + 15 - 6 =42 - 6 = \\3 6$