Question 483542
"joe said, if five times my age in 8 years is subtracted from the square of my present age, the result is 86." find joe's age



let joe's present age be x
so joe's age 8 yrs to this the present time will be x+8,

now that means 5* joe's age in 8yrs is 5(x+8)
the square of his present age is x^2
therefore we can hereby write that
X^2-5(x+8)=86: expanding the bracket we'll have

X^2-5x-40=86

x^2-5x-40-86=0

x^2-5x-126=0

can you predict the factors of this quadratic equation?

try

it"s 14 and 9

x^2-14x+9x-126=0
x(x-14)+9(x-14)=0
(x+9)(x-14)=0

either x+9=0 or x-14=0
the first option gives x=-9 while the second gives x as 14

since joe's age cannot be negative, joe's present age is 14yrs

hope you understand the tricks
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