Question

daca x+ 2y = 17 si y-3z =4 atunci calculati 2x +5y- 3z =? ( 3x +6y ) + (2y - 6 z)= ? ( 2x + 4y) * ( x+ 4y -6z ) = ?

Answer 1

x+ 2y = 17 y-3z =4  a) 2x +5y- 3z =x + x + 2y + 3y - 3z =x + x + 2y + 2y + y - 3z =(x + 2y) + (x + 2y) + y - 3z =
17 + 17 + 4 = 38


( 3x +6y ) + (2y - 6 z)= ? 
3 · (x + 2y) + 2 · (y - 3z) =
3 ·17 + 2 · 4 =
51 + 4
55

( 2x + 4y) * ( x+ 4y -6z ) =
2 · (x + 2y) · (x + 2y + 2y - 6z) = 
2 · (x + 2y) · ((x + 2y) + 2 (y - 3z)) =
2 · 17 · (17 + 2 · 4) = 
34 · (17 + 8) = 
34 · 25 =
850