Cho hàm số bậc nhất y=ax+4 Tìm điểm trên (d) có khoảng cách đến hai trục tọa độ bằng nhau?

By Trang Ánh Nam -

Cho hàm số bậc nhất y=ax+4 Tìm điểm trên (d) có khoảng cách đến hai trục tọa độ bằng nhau?
Giải:
Gọi M (xo ,yo) là điểm cần tìm
Do M thuộc hàm y=ax+4 nên ta có: yo=axo+4
Nếu viết dưới dạng 1 ẩn thì: M=(xo;axo+4)
Do M có khoảng cách đến 2 trục tọa độ bằng nhau nên M thuộc đường thẳng y=x nên ta có:
axo+4=xo <=>(a-1)xo+4=0 (đây là phương trình hoành độ và tung độ của M)
nếu ta viết theo kiểu hệ phương trình thì M là nghiệm của hệ:


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