the sum of reciprocals of a child's age (in years) 3 yrs ago and 5yrs hence from now is 1\3. find his present age
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Answered by
35
The answer is 7 years .....
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praisy1:
srry but i did'nt understand from 3(2x-2)onwatds
srry +2
cross multiply..
thx
( x-3)(x+5) = x²+5x -3x-15
then cross multiply to get the answrr
Brainliest ?
ur judgement..
Answered by
10
let the childs age be x
his age 3 years ago= x - 3 --------------1
his age after 5 years = x +5 ------------2
sum of reciprocal of 1 and 2 ,
1/x-3 +1/x+5 = 1/3
x+ 5 + x -3 1
------------------------ = ---
x^2+5x - 3x -15 3
2 x + 2 1
---------------- = ----
x^2 +2x - 15 3
6x + 6 = x^2 + 2x -15
x^2 - 4x = 21
(x^2-7x) + (3x-21) = 0
x (x-7) + 3 (x-7)=0
thus,
x= 7
x= -3
age cannot be negative.so 7 is the answer
the childs age is 7.
hope it helps!!!
his age 3 years ago= x - 3 --------------1
his age after 5 years = x +5 ------------2
sum of reciprocal of 1 and 2 ,
1/x-3 +1/x+5 = 1/3
x+ 5 + x -3 1
------------------------ = ---
x^2+5x - 3x -15 3
2 x + 2 1
---------------- = ----
x^2 +2x - 15 3
6x + 6 = x^2 + 2x -15
x^2 - 4x = 21
(x^2-7x) + (3x-21) = 0
x (x-7) + 3 (x-7)=0
thus,
x= 7
x= -3
age cannot be negative.so 7 is the answer
the childs age is 7.
hope it helps!!!
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