a+2b= 18
3b-2a=6
Get a=b=6 equilateral.
2. Case 1: If the waist circumference is 8cm, then the lower circumference is 6cm =2*8+6=22cm.
Case 2: If the waist circumference is 6cm, then the circumference of the bottom is 8cm =2*6+8=20cm.
According to the nature that the sum of two sides of a triangle is greater than the third side and the difference between the two sides is smaller than the third side, if both cases are true, the circumference is 22 or 20cm.
3. Case 1: Let the waist circumference be 6cm, then the cardinal number =30-2*6= 18cm. According to the property that the sum of two sides of a triangle is greater than the third side, since 2 * 6 = 12 cm.
Case 2: If the cardinal number is 6cm, the waist circumference =(30-6)/2= 12cm, which is proved by the above properties.
The other two sides are equal to 12cm.
The triangle is isosceles. Set waist a and bottom b,
Case1:a >; b
2a+b= 12
a-b=3
D: a=5 and b=2 are verified by the above-mentioned properties.
Scene 2: A
2a+b= 12
b-a=3
A=3, b=6, because 3+3=6 is not greater than the third side, so this situation is not true.
That is, the length of three times is 5cm, 5cm and 2cm respectively.
5. According to the nature mentioned above.
There are 7+10 >; x，x & lt 17
10-7<x, x> three
, 3
If the three categories are 2, x- 1, 3 respectively.
Have 2+3 > X- 1, x < 6
3-2 & lt； x- 1，x >2
(x- 1)+3 & gt； 2，x & gt0
Get: 2
6, because the side is the longest side, let this side X, then x >；; 7 and x> 10, x> 10.
In addition, 7+10 >: x，x & lt 17,
Get: 10
7. Set the radix X, using x & gt2-2=0, x & lt2+2=4,
Which is 0.
Get 0+4
That is, the circumference is greater than 4 and less than 8.
8. Let waist A and bottom B be 2a+b= 10, and get a=( 10-b)/2. Because a is an integer. So 10-b is an even number. B is an even number.
Take b=2, 4, 6 and 8 in turn.
When b=2, a=4 can be seen from the above formula. Authentication has been established.
When b=4, a=3. Authentication has been established.
When b=6 and a=2. Verification: 2+2 = 4
Therefore, the side lengths of case 1: are 2, 4 and 4 respectively.
Case 1: The side lengths are 4, 3 and 3 respectively.