Question

por favor me ajudeeeeem

Answer 1

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Ola Adriin

a)

2x - y = 7
xy = 4

y = 4/x

2x - 4/x = 7

2x² - 7x - 4 = 0

delta
d² = 49 + 32 = 81
d = 9

x1 = (7 + 9)/4 = 4 ⇒ y1*4 = 4 ⇒ y1 = 1
x2 = (7 - 9)/4 = -1/2 ⇒ y2*(-1/2) = 4 ⇒ y2 = -8

b)

2x - y = 0.1
x*y = 0.15 

y = 2x - 0.1

x*(2x - 0.1) = 0.15 

2x² - 0.1x - 0.15 = 0

delta
d² = 0.01 + 1.2 = 1.21
d = 1.1

x1 = (0.1 + 1.1)/4 = 0.3
x2 = (0.1 - 1.1)/4 = -0.25 

0.3y1 = 0.15
y1 = 1/2

-0.25y2 = 0.15
y2 = -3/5 

c) 

x² + y² = 20
x/y = 2

x = 2y

4y² + y² = 20
5y² = 20
y² = 4

y1 = -2 --> x1 = -4
y2 = +2 --> x2 = 4 

pronto