Qual é o valor numérico da expressão algébrica (x +y) . (x -y) quando X = 2/3 e y = -1? Preciso do cálculo e o resultado!

Each month, a shopkeeper spends 5x + 14 dollars on rent and electricity. if he spends 3x−5 dollars on rent, how much does he spend on electricity? for which value(s) of x is the amount the shopkeeper spends on electricity less than $100? explain how you found the value(s).

If 0° ≤ θ ≤ 90° and cosθ = 11 15 , what is the value of sin (90° - θ)? a) 11 /15 b) 15/ 11 c) 15 /4 d) 4/15

What are the intercepts of x^2+y-9=0