Denise G. answered • 02/04/20

Algebra, College Algebra, Prealgebra, Precalculus, GED, ASVAB Tutor

Your equation is correct.

y=42000(.88)^{x} Plug in 21000 in for y and solve

21000=42000(.88)^{x} Divide both sides by 42000 and simplify

21000/42000=42000/42000(.88)^{x}

0.5=(.88)^{x } Rewrite this a a logarithm.

log _{0.88}(0.5)=x

Using the change of base formula

log(0.5)/log(0.88)=x

**x=5.42 years**