What is the value of the ecpression 2x^2+3xy-4y^2when x=2 and y=-4?

Solve the system of equations. y= 2x y= x^2 - 15

Abouncy ball is released from a certain height. on the first bounce, it travels 32cm. with each subsequent bounce, it travels 9/10 the distance of the previous bounce. what is the total distance that the ball has traveled when it completes its 25th bounce?

3x + 4y = 5 x- 3y = -7 solve by substitution