y = (4*10^8)^2 Both factors in the brackets are squared.
4^2 = 16
(10^8)^2 = 10^(2*8) = 10^16
y = 16 * 10^16
y = 1.6 * 10^1 * 10^16
y = 1.6 * 10^(1 + 16)
y = 1.6 * 10^(17) <<<<<< Answer I'd use the brackets unless instructed not to.
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