Question

método de sustitucion
3x+4y=15
2x+y=5


2b+5c=24
8b-3c=19​

Answer 1

a) 3x+4y=15

b) 2x+y=5

a) 3x+4y = 15

4y = -3x + 15

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

a) y = - $\frac{3}{4}$x + $\frac{15}{4}$

b) 2x+y=5

2x + (-$\frac{3}{4}$x + $\frac{15}{4}$) = 5

2x - $\frac{3}{4}$x = 5 - $\frac{15}{4}$

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

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

X = 1

2x+y=5

2 (1) + y = 5

2 + y = 5

y = 5 - 2

Y = 3

S: (x; y) = (1 ; 3)

1) 2b + 5c = 24

2) 8b - 3c = 19

1) 2b + 5c = 24

2b = -5c + 24

b = -5/2c + 12

2) 8b - 3c = 19

8 (-5/2c + 12) -3c = 19

-40/2c + 96 -3c = 19

-20c -3c = 19 - 96

-23c = -77

c = -77 : (-23)

C = 77/23

1) 2b + 5c = 24

2b + 5 (77/23) = 24

2b + 385/23 = 24

2b = 24 - 385/23

2b = 167/23

b = (167/23) : (2)

B= 167/46

S: (b ; c) = (167/46 ; 77/23)