m = 4d
(m-4)(d-4) = 40
Now just solve for m and d.
mary is now four times as old as her daugter.Four years ago the product of their ages was 40.Find present ages.
3 answers
Daughter is X yrs. old.
Mary is 4x yrs. old.
(x-4)*(4x-4) = 40.
4x^2-4x-16x+16 = 40,
4x^2-20x-24 = 0,
x^2-5x-6 = 0, -6 = -6*1. sum = -5 = B.
(x-6)(x+1) = 0.
x-6 = 0. X = 6.
x+1 = 0. x = -1.
Use X = 6.
4x = 4*6 = 24.
Mary is 4x yrs. old.
(x-4)*(4x-4) = 40.
4x^2-4x-16x+16 = 40,
4x^2-20x-24 = 0,
x^2-5x-6 = 0, -6 = -6*1. sum = -5 = B.
(x-6)(x+1) = 0.
x-6 = 0. X = 6.
x+1 = 0. x = -1.
Use X = 6.
4x = 4*6 = 24.
Final answer is....
5 answers