|2m-n/m+2n|=3，2m-n/m+2n= 3
2 (2m-n)/m+2n-2m-n/m+2n-3 = (2m-n)/m+2n-3 = 3-3 = 0 or -6.
2. Given the line segment AB, extend AB to C so that BC= 1/3AB. D is the midpoint of AC, CD=2cm, and find AB.
AC=2CD=4cm AC=4AB/3=4 AB=3
3. if x-y/x+y =2, find the value of x-y/x+y-2 (x+y)/x-y.
x-y/x+y-2(x+y)/x-y = 2-2× 1/2 = 1
4. The quotient of two opposite numbers (except 0) is the third power of (-1). (This can be answered directly)
5. Calculation:1/2+(1/3+2/3)+(1/5+2/5+4/5)+...+(1/60+2)
= 1/2+ 1+ 1.5+2+2.5+。 . . . + 1770=52229.75
6. It is known that rational numbers A and B satisfy A >；; 0, b<0, | a | < b |, then the correct relationship between these columns is (b).
A.-a & lt； b & lta & lt-b b b & lt； -a & lt； A<- BC-BC & lt-b & lt；; b & lta D.b & lt-a & lt； -b & lt； a
This problem takes a= 1 b=-2 by special value method.
7. The product of the square of the inverse of A and the inverse of the cube of B is half (-a? b？ /2), the coefficient of this algebraic expression is (-1/2) and the degree is (5).
8. The sum of two digits of a two-digit number is 12, and the number on the digit is a, which is (120-9a). After exchanging the positions of digits and tens, the new two digits are (9a+ 12).
9. For rational numbers, define an operation "."and satisfy a. b =3a+b/a-3b, then (-2).7. (-6)=(54/65).
7.(-6)=(2 1-6)/(7+ 18)=3/5 (-2) .(3/5)=(-6+3/5)/(-2-9/5)=54/65
10. Ask the child's age and answer: "9 is less than half my father's age." Asked my father's age, he replied, "Three times older than my child!" Ask the child's age? (Equation, detailed process, it is best to talk about ideas)
Suppose the child's age is X.
Dad's age is 3x+3.
0.5(3x+3)-9=x
x= 15