Question

3x + 3y =18 4x +5y =20 por sustitucion e igualación

Answer 1

Respuesta:

Igualación:

• 3x+3y=18

3y= 18-3x

$y=\frac{18-3x}{3}$

• 4x+5y=20

5y = 20-4x

$y=\frac{20-4x}{5}$

y=y

$\frac{18-3x}{3} =\frac{20-4x}{5}$

a/b = c/d ⇒ a*d = c*b

5(18-3x) = 3(20-4x)

90-15x = 60-12x

90-60 = -12x+15x

30 = 3x

30/3 = x

10 = x

$y = \frac{20-4x}{5}$

$y= \frac{20-4*10}{5}$

$y=\frac{20-40}{5}$

y = -20/5

y = -4

Sustitutiva

• 3x+3y=18

3y=18-3x

$y=\frac{18-3x}{3}$

• 4x + 5y= 20

$4x+5(\frac{18-3x}{3} )=20$

$4x+\frac{90-15x}{3}=20$

4x+30-5x = 20 (Se simplifica)

-x+30=20

-x=20-30

-x=-10

x=10