规定新运算符号*的运算过程为a*b=1/3a−1/4b,则 (1)求5*(-5); (2)解方程2*(2*x)=1*x.

问题描述:

规定新运算符号*的运算过程为a*b=

1
3
a−
1
4
b,则
(1)求5*(-5);
(2)解方程2*(2*x)=1*x.

(1)5*(-5)=

1
3
×5-
1
4
×(-5)=
5
3
+
5
4
=
35
12

(2)∵2*x=
2
3
-
x
4

∴2*(
2
3
-
x
4
)=
2
3
-
1
4
2
3
-
x
4
)=
2
3
-
1
6
+
x
16
=
1
2
+
x
16

1*x=
1
3
-
x
4

1
2
+
x
16
=
1
3
-
x
4

去分母得,24+3x=16-12x,
移项得,15x=-8,
系数化为1得,x=-
8
15