Question

2 calcule o valor numerico das seguintes expressões
a) x³-y² para x=-2 e y=-3

b)2a² b³, para a=-4 e b=-5

os resto das questão estão na imagem mim ajudem porfavor​

Answer 1

2)

a)

${x}^{3}-{y}^{2}={(-2)}^{3}-{(-3)}^{2}=-8-9=-17$

b)

$2{a}^{2}{b}^{3}$

$2.{(-4)}^{2}{(-5)}^{3}=-4000$

c)

$\frac{2 {x}^{3} - 3y }{2} = \frac{2. {( - 3)}^{3} - 3.( - 7) }{2}$

$\frac{ - 54 + 21}{2} =-\frac{33}{2}$

d)

$\frac{ {x}^{2} - 2y}{3x} = \frac{ {( - 5)}^{2} - 2.6 }{3.( - 5)}$

$\frac{25 - 12}{ - 15} =-\frac{13}{15})$

3)

a)

{a-b=5 ×(6)

{2a+6b=1

{6a-6b=30

+ {2a+6b=1

$8a=31 \\ a=\frac{31}{8}$

$\frac{31}{8}-b=5\times8 \\31-8b=40 \\ 8b=31-40$

$8b=-9 \\ b=-\frac{9}{8}$

b)

{a+2b=4×(-3)

{3a+5b=8

{-3a-6b=-12

+ {3a+5b=8

$-b=-4\times(-1) \\ b=4$

$a+2b=4 \\ a+2.4=4 \\ a+8=4 \\ a=4-8 \\ a=-4$

c)

{2x+5y=4×(-2)

{4x-7y=3

{-4x-10y=-8

+ {4x-7y=3

$-17y=-5\times(-1) \\ 17y=5 \\ y=\frac{5}{17}$

$2x+5y=4\\ 2x+5.\frac{5}{17}=4\times17$

$34x+25=68 \\ 34x=68-25 \\ 34x=43 \\ x=\frac{43}{34}$

d)

{3x+4y=5×(5)

{5x-9y=4×(-3)

{15x+20y=25

+{-15x+27y=-12

$47y=13 \\ y=\frac{13}{47}$

$3x+4y=5 \\ 3x+4.\frac{13}{47}=5\times{47}$

$141x+52=235\\ 141x=235-52 \\ 141x=183$

$x=\frac{183}{141}$

e)

{a-b=7×(8)

{3a+8b=3

{8a-8b=56

+{3a+8b=3

$11a=59 \\ a=\frac{59}{11}$

$a-b=7\\ \frac{59}{11}-b=7\times(11) \\59-11b=77$

$11b=59-77 \\ 11b=-18 \\b=-\frac{18}{11}$