k3ateanaKatnBn k3ateanaKatnBn
  • 21-11-2016
  • Mathematics
contestada

If x+y=15 and x-y=25, then what is the value of 2x^2 - y^2?
A) 425
B) 775
C) 825
D) 1,575
E) 1,625 ...?

Respuesta :

mozarth11
mozarth11 mozarth11
  • 21-11-2016
x+y = 15
x-y = 25
------------
2x = 40
x = 40/2
x = 20

y = 15-x
y = 15-20
y = -5

2x² - y² = 
2*20² - (-5)² =
2*400 - 25 = 
800 - 25 = 
775
Answer Link
rybag99
rybag99 rybag99
  • 21-11-2016
The answer is B as since x = 20 and y = -5
Answer Link

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