Prove Cot(a+b)=cotAxcotB-1/cotA+cotB

Find the roots of the polynomial function f(x) = x^3 + 2x^2 + x

Prove that the value of the expression 7^8–7^7+7^6 is divisible by 43.

Gabriel determined that his total cost would be represented by 2.5x + 2y – 2. his sister states that the expression should be x + x + 0.5x + y + y – 2. who is correct? explain.