Show that (0.8a+0.4b)^2=(0.8a-0.4b)^2+1.28ab< br />
please help me solve this asap

Step-by-step explanation:

first

(0.8a+0.4b)^2= (0.8a+0.4b) *(0.8a+0.4b)

=

0.64 a^2 + 0.32 ab +0.32ab + 0.16 b^2=

0.64 a^2 + 0.64ab + 0.16 b^2

second

(0.8a-0.4b)^2+1.28ab

= 0.64 a^2 - 0.64ab +0.16 b^2 + 1.28ab

= 0.64 a^2 + 0.64ab + 0.16 b^2

since the first (left parameters ) equals the second(right side parameters)

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answer: i don't understand it

step-by-step explanation: sorry

investment b is an ordinary annuity with $3,909.64 in the account after one year.

step-by-step explanation: