Question

Calculeaza :                                   a) Daca se stie a +3b = 5 si c=8 calculeaza 4a+7b + 2c =
                                                      b) Daca se stie 2a+3c =5 si 2c +b =7 calculeaza 4a +7b+2c =
a) 5+6+7+.....+52                          c) Daca se stie x+2y=5 si a+3b =6 calculea 2x+4y+12b si
b) 13+14+15+.....+175=                8x+12y+8a+24b =
c)101+102+....+252=                    d)Daca se stei 3x+y =10 si 2y+z=3 calculeaza 9x+5y+z si
d)108+109+0.....+1.140=              3x+5y+2z =

Answer 1

 2a+3c =5 si 2c +b =7 calculeaza 4a +7b+2c =
2a+3c=5     |*2
4a+6c=10
4a+6c+2c+b=4a+7b+2c=10+7=17

5+6+7+8+9+............52=52*53:2-1+2+3+4
=53*26-10
=1368

 Daca se stie x+2y=5 si a+3b =6 calculea 2x+4y+12b
x+2y=5   |*2
2x+4y=10
cine e a?

13+14+15+.....+175= 8x+12y+8a+24b
175*176:2-12*13:2
=15400-78
=15322

)101+102+....+252=252*253:2-101*102:2
=31858-5151
=26707

3x+y =10 si 2y+z=3 calculeaza 9x+5y+z
3x+y=10     |*3
9x+3y=30+2y+z=9x+5y+z=33

108+109+0.....+1.140= 3x+5y+2z =650370-5778=644592