Question

${x}^{2} - 23x + 42$
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Answer 1

${x}^{2} - 23x + 42 = 0 \\ {x}^{2} - 2x - 21x + 42 = 0 \\ x(x - 2) - 21(x - 2) = 0 \\ (x - 21)(x - 2) = 0$

hope it helps you

Answer 2

$\huge\bold{Answer:}$

x² - 23x + 42

= x² - ( 21 + 2 ) x + 42

= x² - 21x - 2x + 42

= x ( x - 21 ) - 2 ( x - 21 )

= ( x - 21 ) ( x - 2 )