(a + b - 5) - (a + b - c) = c - 1 (a + b + 7) - (b + d - 3) + (d - a - 10) = c - b giúp mik với hứa vote 5* và hay nhất ạ

1 câu trả lời

$\left(a\:+\:b\:-\:5\right)\:-\:\left(a\:+\:b\:-\:c\right)\:=\:c\:-\:1$

$⇒a+b-5-a-b+c=c-1$

$⇒a+b-5-a-b+c-c=c-1-c$

$⇒a+b-5-a-b=-1$

$⇒b-b+a-a-5=-1$

$⇒a-a-5=-1$

$⇒-5=-1(ktm)$

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$\left(a+b+7\right)-\left(b+d-3\right)+\left(d-a-10\right)=c-b$

$⇒a+b+7−b−d+3+d−a−10=c−b$

$⇒a+b+7-b-d+3+d-a-10+b=c-b+b$

$⇒a+b+7-d+3+d-a-10=c$

$⇒-d+d+a-a+b+7+3-10=c$

$⇒a-a+b+7+3-10=c$

$⇒b+7+3-10=c$

$⇒b=c$ $⇒c=b$