(A) To expand $(a - 2b + 7c)^2$,we use the algebraic identity: $(x + y + z)^2 = x^2 + y^2 + z^2 + 2xy + 2yz + 2zx$.Here,$x = a$,$y = -2b$,and $z = 7c$

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$a^2 + 4b^2 + 49c^2 - 4ab - 28bc + 14ca$

(A) To expand $(a - 2b + 7c)^2$,we use the algebraic identity: $(x + y + z)^2 = x^2 + y^2 + z^2 + 2xy + 2yz + 2zx$.Here,$x = a$,$y = -2b$,and $z = 7c$.Substituting these values into the identity:$(a - 2b + 7c)^2 = (a)^2 + (-2b)^2 + (7c)^2 + 2(a)(-2b) + 2(-2b)(7c) + 2(7c)(a)$.Calculating each term:$= a^2 + 4b^2 + 49c^2 - 4ab - 28bc + 14ca$.