Question

find the value of k for which the polynomial
${x}^{3} - 3 {x}^{2} + 3x + k$
has 3 as its zero

Answer 1

As 3 is its zero, that means x=3. Put value of x as 3.
Therefore,
3^3 - 3×3^2 + 3 ×3 + k = 0
=> 27-27+9+k =0
=> k=-9

Answer 2

$hey \: mate \: here \: is \: your \: answer...$
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${x}^{3} - 3 {x}^{2} + 3x + k = 0 \\ \\ on \: putting \: x = 3 \\ \\ (3) {}^{3} - 3(3) {}^{2} + 3(3) + k = 0 \\ \: \: \: \: \: \: \: \: \: \: \: 27 - 3(9) + 9 + k = 0 \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: 27 - 27 + 9 + k = 0 \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: 9 + k = 0 \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: k = - 9$

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$hope \: it \: helps....$