Question

the coefficient of x2 in the expansion of (x+5) )(x+6) (x+7)
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Answer 1

Step-by-step explanation:

(x+5)(x+6)(x+7)

Let a=5 b=6 and c=7

(x+a)(x+b)(x+c)

x³+(a+b+c)x²+(ab+bc+ac)x+abc

Coeff of x²=(5+6+7)=18