Question

Un copil socoteste ca in urma cu 4 ani tatal sau era de patru ori mai in varsta decat el,iar peste 12 ani tata va fi de doua ori mai in varsta ca el.Ce


varsta are tatal si ce varsta are fiul?

Answer 1

$\left \{ {{4(c-4)=t-4} \atop {2(c+12)=t+12}} \right.$
4c-16=t-4 ⇒ 4c-t=12
2c+24=t+12 ⇒ 2c-t=-12
$\left \{ {{4c-t=12} \atop {2c-t=-12}} \right.$
inmultesti a doua ecuatie cu (-1)
$\left \{ {{4c-t=12} \atop {-2c+t=12}} \right.$
acum le aduni si obtii : 2c=24 ⇒ c=12
4*12-t=12 ⇒ 48-t=12⇒ t=36