7x2+3x547{x}^{2}+3x-54

1
Split the second term in 7x2+3x547{x}^{2}+3x-54 into two terms.
7x2+21x18x547{x}^{2}+21x-18x-54

2
Factor out common terms in the first two terms, then in the last two terms.
7x(x+3)18(x+3)7x(x+3)-18(x+3)

3
Factor out the common term x+3x+3.
(x+3)(7x18)(x+3)(7x-18)

Done

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