Question

exercitiile 13 si 14
multumesc :)

Answer 1

13. a) |x - 1| + |y + 3| = 0

x - 1 = 0 /+1
x = 1  

y + 3 = 0 /-3
y = -3

b) |2x + 4| + |3y + 9| = 0 

2x + 4 = 0 /-4
2x = -4 /:2
x = -2

3y + 9 = 0 /-9
3y = -9 /:3
y = -3

14. a) a + b = -21
a/b = 4/3 ⇔ 3a = 4b ⇒ a = 4b/3
~
a, b = ?
~
a + b = -21
4b/3 + b = -21
(4b + 3b) : 3 = -21
7b/3 = -21 /·3
7b = -63 /:7
b = -9

a = 4b/3 = (-9 · 4) : 3 = -12

b) a · b = 8 
a/b = 2 ⇒ a = 2b
~
a, b = ?
~
a · b = 8 
2b · b = 8 
2b² = 8 /:2
b² = 4 
b² = 2²
b = 2 

a = 2b = 4

/robertinni

Answer 2

13.
a)
|x-1| + |y+3|=0
|x-1| =0
x-1=0 |+1
x=1

|y+3|=0
y+3=0 |-3
y=-3


b)
|2x+4| + |3y+9|=0

|2x+4|=0
2x+4=0 |-4
2x=-4 |:2
x=-2

|3y+9|=0
3y+9=0 |-9
3y=-9 |:3
y=-3


14.
a)
Notez a si b numerele; a,b€Z

a+b=-21

a/b=4/3 => a/4=b/3=(a+b)/(4+3)=-21/7=
=-3
=>a=4×(-3)=-12
=>b=3×(-3)=-9

b) Notez cu x si y numerele; x,y€Z

x·y=8

x/y=2 =>x=2y

Inlocuim:
2y·y=8 |:2
y^2=4
y^2=2^2
=>y=2 =>x=2×2=4