It is proved that the false propositions a, B and C are three points on the same line, then AB + BC = AC

To prove a false proposition, just give a counterexample
When a, B and C are in the same horizontal line and a, B and C are from left to right, a, C and B do not conform to the conclusion
(Note: if the conclusion of the topic is line segment, it is done like this, but if it is vector, it is the real problem.)

RELATED INFORMATIONS

1. (a+b+c)(a^2+b^2+c^2-ab-ac-bc)+3ab=
2. Calculate the square of (AB) divided by the square of (BC) multiplied by the square of (AC)
3. As shown in the figure, it is known that a, B and C are on the same straight line, ab = 24cm, BC = 38ab, e is the midpoint of AC, D is the midpoint of AB, find the length of de
4. As shown in the figure, it is known that a, B and C are on the same straight line, ab = 24cm, BC = 38ab, e is the midpoint of AC, D is the midpoint of AB, find the length of de
5. It is known that a, B and C are on the same straight line. AB = 24cm, BC = 3 / 8 AB, e is the midpoint of AC, D is the midpoint of AB, and the length of De is calculated It's done tonight
6. Given that ABC three points are on the same straight line, ab = 100 cm, BC = 3 / 5 AB, e is the midpoint of AC, find the length of be? It's better now. I can use it
7. Given that ABC three points are on the same straight line, ab = 100 cm, BC = 3 / 8 AB, e is the midpoint of AC, find the length of be?
8. If the line segment AB is extended to point C so that BC = 2 / 3AB and point D is the midpoint of AC, then CD = 3, then the length of AB is longer
9. Given the segment AB, extend AB to C so that BC = 13ab, D is the midpoint of AC, DC = 2cm, then the length of segment AB is () A. 3B. 6cmC. 4cmD. 3cm
10. Given the line segment AB = a, extend AB to point C so that BC = 1 / 3AB and point D is the midpoint of line segment AC. (1) find the length of CD. (2) if BD = 2 cm, find the length of ab .______ .___ ._. a d b c
11. Given three points a, B and C, according to the following conditions, can a, B and C determine a circle? If you can, request the radius; if you can't, please explain the reason. (1) AB = [63 + 4] cm, BC = 123cm, AC = [63-4] cm; (2) AB = AC = 10cm, BC = 12cm
12. In tetrahedral a-bcd, ab ⊥ CD, AC ⊥ BD, prove ad ⊥ BC It shouldn't be very difficult, but I just can't. help
13. A. B, C and D are the four points in space, and ab is perpendicular to CD, ad is perpendicular to BC Please give me a diagram, if it's good, I can add more points.
14. It is known that BD = AC + CD, ad ⊥ BC is d. please guess the relationship between ∠ B and ∠ C and prove it Obtuse angle △ ABC, ad is the height on the edge of BC, BC is the longest edge
15. It is known that in the isosceles RT triangle ABC, ∠ ACB = 90 °, D is the midpoint of BC, e is the point on AB, and AE = 2EB, the proof of ad ⊥ CE is obtained
16. In △ ABC, it is known that ab = L, ∠ C = 50 ° and the length of BC reaches the maximum when ∠ B =
17. In △ ABC, it is known that ab = 2, ∠ C = 50 ° when ∠ B=_____ The length of. BC reaches the maximum when the In △ ABC, it is known that ab = 2, ∠ C = 50 ° when ∠ B=_____ The length of. BC reaches the maximum when the It's better to have process analysis, ideas and so on
18. In the triangle ABC, ab = 2 ∠ C = 50 ° when ∠ B = what is the maximum length of BC
19. In the triangle ABC, we know that B = 45 °, D is the point on BC, ad = 7, AC = 8, DC = 3, and find the length of ab
20. The proof of inequality, Verification: A ^ 2 + B ^ 2 + C ^ 2 ≥ AB + BC + Ca