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+1 vote
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in Polynomials by (350 points)
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If -4 is a root of the equation x2+mx-4=0 and the equation x2+mx+a=0 has equal roots, then find 4a.

1 Answer

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Best answer

\(\because\) '-4' is root of equation x2 + mx - 4 = 0

\(\Rightarrow\) 16 - 4m -4 = 0 \(\Rightarrow\) 4m = 12 \(\Rightarrow\) m =3

Now,

x2 + mx + a = 0 \(\Rightarrow\) x2 + 3x + a = 0 

has equal roots

Then, b2 - 4ac = 0

\(\Rightarrow\) 9 - 4a = 0

\(\Rightarrow\) 4a = 9

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