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The present age of elder and younger brothers are 13 yrs and 7 yas respectively. In how many years will the product of their agel be 280? Solv​

User Fafaro
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Answer:

....x = the number of years sought

in x years the eldest will have x+13, the youngest x+7

we are looking in how many years the product of their ages will be 280

(x+13)(x+7)=280

x²+7x+13x+91=280

x²+20x+91-280 =0

x²+20x-189 =0

b²-4ac = 20²-4(1*-189)=1156

Δ=1156; √Δ=34

(-b-√Δ)/2a =(-20-34)/2=-27

(-b+√Δ)/2a = (-20+34)/2 =7

the number of years cannot be negative

it is in 7 years that the product of their ages will be 280

to be checked :

(13+7)(7+7) = 20*14=280

Explanation:

User Ebryn
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