Question

x=3 is a root of the quadratic equation 7× square - ( k+1 ) +3 = 0 if k =? ​

Answer 1

Answer:

$p(x) = 7 {x}^{2} - (k + 1)x + 3 \: where \: x = 3 \\ p(x) = 0 \\ 7( {3})^{2} - (k + 1)3 + 3 = 0\\ 7 \times 9 - 3k - 3 + 3 = 0 \\ 63 - 3k = 0 \\ - 3k = - 63 \\ k = \frac{ - 63}{ - 3} \\ k \: = 21 \\ If \: k =21 \: then \: x=3 \: is \: a \: root \: of \: the\: quadratic \: equation \: 7 {x}^{2} - (k + 1)x + 3 \: .$

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