x^2 - 3^2 = 4^2
=> x^2 - 9 = 16
=> x^2 = 16 + 9
=> x^2 = 25
=> x^2 = 5^2
=> x = 5
x2-32=42
=>x2=42+32
=>x2=25=52=(-5)2
=>x E {-5;5}
x2-32=42
=>x2-9=16
=>x2=16+9
=>x2=25
=>x thuộc {-5;5}
x2-32=42
=> x^2 - 9 = 16
x^2= 16+9
x^2=25
x^2=5^2
=> x=5
X^2 - 3^2 = 4^2
=> X^2 - 9 = 16
=> X^2 = 16 + 9
=> X ^2 = 25
=> x^2 = 5*2
=> x = 5