Respostas
respondido por:
3
{x+2y=-7 ⇒x=-7-2y
{x.y=-15
(-7-2y)y=-15
-7y-2y²=-15
-2y²-7y+15=0 x(-1)
2y²+7y-15=0
y=-7(+ ou -)√49-4.2.(-15)
----------------------------------
4
y= -7+ ou -√49+120 -7 + ou -√169 6 20
-----------------------= --------------------= y'= ----- =1,5 e y"=- ----= -5
4 4 4 4
x=-7-2y
x=-7-2.1,5= -7-3=-10
x= -7-2(-5)=-7+10=3
{x.y=-15
(-7-2y)y=-15
-7y-2y²=-15
-2y²-7y+15=0 x(-1)
2y²+7y-15=0
y=-7(+ ou -)√49-4.2.(-15)
----------------------------------
4
y= -7+ ou -√49+120 -7 + ou -√169 6 20
-----------------------= --------------------= y'= ----- =1,5 e y"=- ----= -5
4 4 4 4
x=-7-2y
x=-7-2.1,5= -7-3=-10
x= -7-2(-5)=-7+10=3
respondido por:
8
a)x + 2y = -7 → x = -7-2y
x . y = -15
--------------
(-7-2y).y = -15
-7y - 2y² = -15
-2y² - 7y + 15 = 0 .(-1)
2y² + 7y - 15 = 0
Δ=49-4.-2.15 y'=-7+13 y''=-7-13
Δ=49+120 -------- -------
Δ=169 2.2 2.2
y'=6/4 y''=-20/4
y'= 3/2 y''=-5
↓ ↓
x = -7-2y x = -7-2.(-5)
x = -7-2.(3/2) x = -7 + 10
x = -7- 3 x = 3
x = -10
b) x = 2 - y
x² + y² = 10
-----------------
(2-y)² + y² = 10
4 - 4y + y² + y² = 10
2y² - 4y + 4 - 10 =0
2y² - 4y - 6 = 0 (÷2)
y² - 2y - 3 = 0
Δ=4-4.1.-3 y'=2+4 y''=2-4
Δ=4+12 ------ ------
Δ=16 2 2
y'=6/2 y''=-2/2
y'=3 y''=-1
↓ ↓
x= 2-y x = 2-y
x = 2-3 x = 2-(-1)
x = -1 x = 2+1
x = 3
c) x - y = 11 → x =11+y
y² - x = - 5
----------------
y² - (11+y) + 5 = 0
y² - 11 - y + 5 = 0
y² - y - 6 = 0
Δ=1-4.1.-6 y'=1+5 y''=1-5
Δ=1+24 ----- -----
Δ=25 2 2
y'=6/2 y''=-4/2
y'=3 y''=-2
↓ ↓
x = 11+y x = 11+y
x = 11+3 x = 11-2
x = 14 x = 9
x . y = -15
--------------
(-7-2y).y = -15
-7y - 2y² = -15
-2y² - 7y + 15 = 0 .(-1)
2y² + 7y - 15 = 0
Δ=49-4.-2.15 y'=-7+13 y''=-7-13
Δ=49+120 -------- -------
Δ=169 2.2 2.2
y'=6/4 y''=-20/4
y'= 3/2 y''=-5
↓ ↓
x = -7-2y x = -7-2.(-5)
x = -7-2.(3/2) x = -7 + 10
x = -7- 3 x = 3
x = -10
b) x = 2 - y
x² + y² = 10
-----------------
(2-y)² + y² = 10
4 - 4y + y² + y² = 10
2y² - 4y + 4 - 10 =0
2y² - 4y - 6 = 0 (÷2)
y² - 2y - 3 = 0
Δ=4-4.1.-3 y'=2+4 y''=2-4
Δ=4+12 ------ ------
Δ=16 2 2
y'=6/2 y''=-2/2
y'=3 y''=-1
↓ ↓
x= 2-y x = 2-y
x = 2-3 x = 2-(-1)
x = -1 x = 2+1
x = 3
c) x - y = 11 → x =11+y
y² - x = - 5
----------------
y² - (11+y) + 5 = 0
y² - 11 - y + 5 = 0
y² - y - 6 = 0
Δ=1-4.1.-6 y'=1+5 y''=1-5
Δ=1+24 ----- -----
Δ=25 2 2
y'=6/2 y''=-4/2
y'=3 y''=-2
↓ ↓
x = 11+y x = 11+y
x = 11+3 x = 11-2
x = 14 x = 9
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