Question

For what value of a, ax^2+8xy+8y^2=0 represents a pair of coincidenct straight lines?​

Answer 1

$for \: pair \: of \: straight \: lines \\ \\ a {x}^{2} + 2hxy + b {y}^{2} = 0 \\ \\ the \: condition \: is \\ \\ {h}^{2} = ab \\ \\ here \\ \\ a {x}^{2} + 8xy + 8 {y}^{2} = 0 \\ \\ {4}^{2} = 8a \\ \\ a = 2$

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