# If -4 is a root of the equation x2 +px -4=0 and the equation 2x2 +px +k=0 has equal roots find 'k'If -4 is a root of the equation x2 +px -4=0 and the equation 2x2 +px +k=0 has equal roots find 'k'

If -4 is the root of the eqn x2 + px -4 = 0
=> x = 14
=> -4 x -4 + p x -4 -4 = 0
=> 16 - 4p - 4 = 0
=> -4p = -12
=> p = 3
Now, second eqn has equal roots
=> b2 - 4ac = 0
=> p2 - 8k  = 0
=> -8k  = -9
=> k = 9/8
I am not sure about the calculation, so plz check it out again, otherwise the procedure is correct :D
• 4
anyway thank you for the answer
• -3
Hey!!! I am harsh If -4 is the root of the equation x^2+px-4=0 x^2+px-4=0 Put x= -4 -4×-4+px-4=0 16-4p-4=0 -4p+12=0 -4p=-12 P=-12/-4 P=3 Now second equation has equal roots P(x^2+x)+k=0 Px^2+px+k=0 Put a=p b=p c=k b^2-4ac=0 p^2-4×p×k=0 p^2-4pk=0 Put p=3 3×3-4×3×k=0 9-12k=0 -12k=-9 K=-9/-12 K=9/12 K=3/4 \$\$\$\$\$ I hope that this answer will help you in your studies. \$\$\$\$\$
• 0
Yes thanks alot
• -1
alpha *beta = -4
beta =1
p= -4+1 = -3
b^2 -4ac =0 for equal roots
p^2-8k=0
9-8k=0
k=9/8
• -1
What are you looking for?