Question 433248
If Marty's speed is set equal to x, then:
270/x=(270/(x+15))+1.5
Multiply all by x(x+15), we get:
270(x+15)=270x+1.5(x2+15x)
270x+4050=270x+1.5x2+22.5x
0=1.5x2+22.5x-4050
Divide by 1.5:
0=x2+15x-2700
0=(x+60)(x-45)
x=-60,45
Throwing out the negative result, we get Marty's speed to Memphis as 45mph.
*[invoke quadratic "x", 1, 15, -2700 ]