a+b+c=14 suy ra: 7a+7b+7c=14.7=98
suy ra: 9a+8b+6c-7a-7b-7c=101-98
suy ra: (9a-7a)+(8b-7b)+(6c-7c)=3
suy ra: 2a+b+-c=3
suy ra: 2a+b-c=3
Ta có : a+b+c=14 => a+b=14-c (1) và 9a+8b+6c=101 (2)
Thay (1) vào phương trình 9a+8b+6c=101 ta được:
9a+8b+6c=101<=>a+8(a+b)+6c=101<=> a+8(14-c)+6c=101<=>a+112-8c+6c=101<=>a-2c=-11<=>7(a-2c)=-77<=>7a-14c=-77(2)
Lấy (2) cộng (3) vế theo vế ta được:
16a+8b-8c=24<=>8(2a+b-c)+24<=>2a+b-c=3
\(9a+8b+6c=3a+2b+6a+6b+6c=3a+2b+6\cdot14=3a+2b+84=101\)
\(\Rightarrow3a+2b=17=14+3=a+b+c+3\Rightarrow3a+2b-a-b-c-3=0\)
\(\Rightarrow2a+b-c-3=0\Rightarrow2a+b-c=3\)
a + b + c = 14
=> 7a + 7b + 7c = 14.7 = 98
=> 9a + 8b + 6c - 7a - 7b - 7c = 101 - 98
=> ( 9a - 7a ) + ( 8b - 7b ) + ( 6c - 7c ) = 3
=> 2a + b - c = 3
=> 2a + b - c = 3
