Please help?

Simplify: (4a−2b)(a+b) 4a2−8ab−2b2 4a2−6ab−2b2 4a2+2ab−2b2 4a2−2ab−2b2

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?

Find cot x if sin x cot x csc x = √2

Anyone know these questions? i need ,.