已知2x+5y+4z=15,7x+y+3z=14,则4x+y+2z的值为_.
问题描述:
已知2x+5y+4z=15,7x+y+3z=14,则4x+y+2z的值为______.
答
由于2x+5y+4z=15,7x+y+3z=14;
令4x+y+2z=m(2x+5y+4z)+n(7x+y+3z)=(2m+7n)x+(5m+n)y+(4m+3n)z;
由于左边=右边,则可列方程组
;解得:
2m+7n=4 5m+n=1 4m+3n=2
.
m=
1 11 n=
6 11
因此4x+y+2z=m(2x+5y+4z)+n(7x+y+3z)=
×15+1 11
×14=9.6 11
故答案为:9.