Michael D. answered • 07/17/19
Versatile STEM tutor eager to teach
Let
A = age now
"My age in 10 years" can signify +10, but "10 years ago" is -10.... I'm assuming you meant "10 years ago" which is (-10)
From the word problem you get :
(A - 10)2 = 5*A
Solve :
(A - 10)2 = 5*A
A2 - 20*A + 100 = 5*A
A2 - 25*A + 100 = 0
(A - 20) * (A - 5) = 0
A = 5 & 20
Since you wouldn't have an age 10 years ago at 5 years old (you can't be -5 years old...), 20 is the only viable option.
The person is 20 years old!!
PS : If you would of done "My age in 10 years" which signifies +10 then the equation would of been
(A + 10)2 = 5*A
A2 + 20*A + 100 = 5*A
A2 + 15*A + 100 = 0
This doesn't have real roots. The roots are imaginary (have 'i' in them) and thus cannot be someone's age at all...
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Always check your work!!
(A - 10)2 = 5*A
(20 - 10)2 = 5*20
102 = 100
100 = 100 CORRECT!
