Question

ПОМОГИТЕ!
${x}^{2} + x + neznauy$
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Answer 1

$x^2+\underbrace {x}_{2ax}+\underbrace {?}_{a^2}=(x+a)^2\\\\2ax=x\; \; \Rightarrow \; \; 2a=1\; ,\; \; a=\frac{1}{2}\; \; \; \Rightarrow \; \; \; a^2=\frac{1}{4}\\\\x^2+x+\frac{1}{4}=(x+\frac{1}{2})^2$