Question

Resolva as equações
A) 7x-15=x-3x-15
B) (y+2)(y-4)+(y-3)(y+1)=2y²+2y+7
C) -2(x+5)+3x=-7x-(2-4x)
D) x+2(15-3x)=-10
E) 7x-13=9-5x

Answer 1

A)7x-15=x-3x-15
7x-x+3x=-15+15
9x=0
x=0/9
x=0

B)(y+2).(y-4)+(y-3).(y+1)=2y²+2y+7
y²-4y+2y-8+y²+y-3y-3=2y²+2y+7
y²-4y+2y+y²+y-3y-2y²-2y=7+8+3
-8y=18 . (-1)
8y=-18
y=-18/8
y=-2,25

C) -2(x+5)+3x=-7x-(2-4x)
-2x+10+3x=-7x-2+4x
-2x+3x+7x-4x=-2-10
4x=-12
x=-12/4
x=-3

D) x+2(15-3x)=-10
x+30-6x=-10
x-6x=-10-30
-5x=-40 .(-1)
5x=40
x=40/5
x=8

E) 7x-13=9-5x
7x+5x=9+13
12x=22
x=22/12
x=1,83

Answer 2

A) 7x-15=x-3x-15 ==>  7x-x+3x = -15+15 ==> 9x=0 ==> x = 0

B) (y+2)(y-4)+(y-3)(y+1)=2y²+2y+7

 (y+2)(y-4)+(y-3)(y+1) - 2y² - 2y - 7 = 0

y² - 4y + 2y - 8 + y² + y - 3y - 3 - 2y² - 2y - 7 = 0

 - 4y - 8 + y - 3y - 3 - 7 = 0

 - 3y - 18 = 0 ==> -3y = 18(-1)

3y = - 18 ==> y = - 6
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C) -2(x+5)+3x=-7x-(2-4x)

 -2x - 10 + 3x = - 7x - 2 + 4x  ==> x - 10 = - 3x - 2 

x + 3x = - 2 + 10 ==> 4x = 8 ==> x = 2
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D) x+2(15-3x)=-10

 x + 30 - 6x = - 10 ==> - 5x = - 10 - 30

- 5x = - 40(-1) ==> 5x = 40 ==> x = 8
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E) 7x-13=9-5x

7x - 5x = 9 + 13

2x = 22

 x = 11