Cho tam giác ABC có góc A bằng 90 độ, đường cao AH. Kẻ HM vuông góc AB tại M, HN huống góc AC tại N. Chứng minh. a) Am. Ab=AN. AC=HB. HC b) AM. AB+AN. AC=2MN²

Lin is writing an equation to model the proportional relationship between y, the total cost in dollars of downloading videos from a website, and x, the number of videos downloaded. she knows that the total cost to download 3 videos was $12. her work to find the equation is shown below. joylin’s work step 1 k= 3/12= 0.25 step 2 y= 0.25x where did joylin make her first error?