Question

 alguem sabe fazer essas contas

 

X² -90=31

 

5X² + 4=49

 

2X² + 11=X² +12

 

5 (X² - 1)+4 (X² + 1)

 

X (X + 2)=2X + 25

Answer 1

x² - 90 = 31
x² = 31 + 90
x² = 121
x =  ±  √121
x = ± 11

S[- 11, + 11]


5x² + 4 = 49
5x² = 49 - 4
5x² = 45   ÷ 5
x² = 9
x =  ± √9
x =  ±  3

S[- 3 , + 3]


2x² + 11= x² + 12
2x² - x² = 12 - 11
x² = 1
x = ± √1
x = ±  1

S[- 1, + 1]


5.(x² - 1) + 4.(x² + 1) = 0
5x² - 5 + 4x² + 4 = 0
5x² + 4x² = + 5 - 4
9x² =  + 1
 x = ±  √1
          √9

x = ± 1
         3

S[ - 1/3  ,  + 1/3]



x.(x + 2) = 2x + 25
x² + 2x = 2x + 25
x²  + 2x - 2x - 25 = 0       elimina + 2x - 2x 
x² - 25 = 0
x² = + 25
x =  ± √25
x =  ±  5

S[- 5 , + 5]