Question

factorise x^2 - 23x + 42

Answer 1

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

Answer 2

Hey friend your answer is here.
${x}^{2} - 23x + 42 \\ = {x}^{2} - 21x - 2x + 42 \\ = x(x - 21) - 2(x - 21) \\ (x - 21)(x - 2)$