Question
Simplify:
$(a + b + c)^2 + (a - b + c)^2$

Answer

In the given problem,
we have to simplify the expressions
Given $(a + b + c)^2 + (a - b + c)^2$ By using identity $(x + y + z)^2 = x^2 + y^2 + z^2 + 2xy + 2yz + 2zx$
Hence the equation becomes
$\big(\text{a}+\text{b}+\text{c}\big)+\big(\text{a}\text{b}+\text{c}\big)\\=\Big[\text{a}^2+\text{b}^2+\text{c}^2+2\text{ab}+2\text{bc}+2\text{ca}\Big]\\+\Big[\text{a}^2+(-\text{b})^2+\text{c}^2+2\text{a}(-\text{b})+2(-\text{b})(\text{c})+2\text{ca}\Big]$
$=\text{a}^2+\text{b}^2+\text{c}^2+2\text{ab}+2\text{bc}+2\text{ca}\\+\text{a}^2+\text{b}^2+\text{c}^2-2\text{ab}-2\text{bc}+2\text{ca}$
$=\text{a}^2+\text{a}^2+\text{b}^2+\text{b}^2+\text{c}^2+\text{c}^2\\+2\text{ab}-2\text{ab}+2\text{bc}-2\text{bc}+2\text{ca}+2\text{ca}$
$=2\text{a}^2+2\text{b}^2+2\text{c}^2+4\text{ca}$
Talking 2 as common factor we get$=2\big(\text{a}^2+\text{b}^2+\text{c}^2+2\text{ca}\big)$
Hence the simplified value of $\big(\text{a}+\text{b}+\text{c}\big)^2+\big(\text{a}-\text{b}+\text{c}\big)^2$ is $2\big(\text{a}^2+\text{b}^2+\text{c}^2+2\text{ca}\big).$

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