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2013-12-14T19:18:23+01:00
X = √72 = √2*36  = 6√2
y = √98 = √2*49 = 7√2
 

x
² - y² = (√72)² - (√98)²
x
² - y² = 72 -98 = -26

x + y = 6√2 + 7√2
x + y = √2( 6 + 7) 
x + y = √2( 13) 
x + y = 13√2