If a and b are two positive numbers such that $4a^2 + b^2 = 20$ and ab = 4, then the value of 2a + b is :
Answer & explanation
Correct answer: option 3
$4a^2 + b^2 = 20$
ab = 4,
then the value of 2a + b is= ?
( a + b )2 = a2 + b2 + 2ab
( 2a + b )2 = 4a2 + b2 + 4ab
( 2a + b )2 = 20+ 4(4)
( 2a + b )2 = 36
2a + b= 6