Question

rezolvati prin metoda substitutiei :
3a+4b=7
-2a+3b=5

Answer 1

Metoda substitutiei=inlocuire
3a=7-4b
a=(7-4b)/3
$-2( \frac{7-4b}{3} )+3b=5 \\ -2(7-4b)+9b=15 \\ -14+8b+9b=15 \\ 17b=15+14 \\ 17b=29 \\ b=17/10 \\ a=(7-4*17/10)/3 \\ a=1/15 \\ Verificare: 3* \frac{1}{15}+4* \frac{17}{10} = \frac{1}{5}+ \frac{68}{10} = \frac{2}{10} + \frac{68}{10} = \frac{70}{10} =7$