S k = 4 a solution of 4 k + 7 = 7 k-1?

What is the graph of the absolute value equation ? y=|x|-5

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )

Cos^2x+cos^2(120°+x)+cos^2(120°-x)i need this asap. pls me