Question

If one root of x2+ax+8=0 is 4 and the equation x2+ax+b=0 jas equal roots then b=

Answer 1

if root of equation is 4 So, x= 4, by put this in equation we get (4)^2 +a(4) + 8 =0 => 16 + 4a +8 = 0 => 24 + 4a = 0 => 4a= -24 => a = -6. So, by a= -6 and x= 4 in equation (ii) we get (4)^2 + (-6)(4) + b= 0 => 16 - 24 +b = 0 => -8 +b = 0 => b= 8. please please mark me as brainliest

Answer 2

Answer:

9

Step-by-step explanation:

ANSWER

x  

2

+ax+8=0 has one of it roots as 4

⇒4  

2

+4a+8=0

⇒4[4+a+2]=0

⇒6+a=0

⇒a=−6

Now, the equation  

⇒x  

2

+ax+b=0

    x  

2

−6x+b=0

has double ( equal ) roots.

In a quadratic equation, the roots will be equal if and only if the discrimination (D)=0

Now, the discriminant of the above quadratic equation is  

⇒D=B  

2

−4AC=0

⇒6  

2

−4.1.b=0

⇒6  

2

=4b

⇒b=  

4

36

​  

=9

∴a=−6  and   b=9

Hence, the answer is 9.