Question

3) The roots of x² + 10x+ 21 = 0 are,
a) -3,7 b) 3,-7 c) -3,-7 d) 3,7.​

Answer 1

Answer:

The roots of the given quadratic equation are

$\boxed{\red{\sf\:x\:=\:-7}}\:\sf\:\:or\:\:\boxed{\red{\sf\:x\:=\:-3}}$

Step-by-step explanation:

The given quadratic equation is

x² + 10x + 21 = 0.

x² + 10x + 21 = 0

⇒ x² + 7x + 3x + 21 = 0

⇒ x ( x + 7 ) 3 ( x + 7 ) = 0

⇒ ( x + 7 ) ( x + 3 ) = 0

⇒ x + 7 = 0 or x + 3 = 0

⇒ x = -7 or x = -3.