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Answer:
B= 18x
Step-by-step explanation:
use identity : (a+b)² = a²+2ab+b² you have a =3x and b =3 so: B =2ab
the second term of this trinomial is : 2ab means : 2(3x)(3) = 18x
(3x +3)2=9x2+2(3x)(3)+3²