Andrew M. answered • 04/03/17

Tutor

New to Wyzant
Mathematics - Algebra a Specialty / F.I.T. Grad - B.S. w/Honors

If Slider is x years old

Changeup is x+4 years ld

x(x+4) = 21

I can see the answer is 3 and 7 years old

but let's finish the algebra:

x

^{2}+ 4x = 21x

^{2}+ 4x - 21 = 0(x+7)(x-3) = 0

x = -7 or x= 3

discarding the negative,

Slider is 3 years old.

Changeup is 3+4 = 7 years old