Your question does not clear the purpose of your purchase, so the answer to it will be generic or in general. As developers need different configuration and gamer's need different.
There are many brand in market that are trust worthy. Following are few names :
Laptops within 45K to 50K (price may vary due to GST):
1 Dell Inspiron 15 3000 Core i5 5th Gen
2 Lenovo Z51-70 Core i5 5th Gen
3 HP Core i5 6th Gen
Parameter's to Consider :
1 Processor - Core i5 6Gen to Core i5 6Gen
2 RAM - 4GB to 8GB
3 1TB Hard disk
4 Graphics Card
5 Screen size
7 Operating System
Look for following in the price you are paying :
Screen size : 15.6"
RAM : 6 to 8 GB
Graphics : 2GB (AMD or NVIDIA)
OS : Prefer Win 7 if you are developer/gamer. For casual work you can go for Window 8, 8.1 and 10 as well.
Hard Disk : 1TB
Processor : Core i5 5th Gen at-least.
1 Build quality
2 Service center
So looking for this Dell Laptop is in win win condition. Best support , build quality and Accidental damage protection with the desire configuration.
WHERE TO BUY:
1 Buy it from any computer shop that is know for good service.
2 Any e-commerce site. Look for return policy/support if purchasing online.