Question

the product of rena age (in year) 5 year ago and her age 8 year later is 30 .find her present age .​

Answer 1

Answer:

Rena is  7 yrs old

Step-by-step explanation:

let the Age of Rena is A

then,

(A-5) * (A+8) = 30

A² + 8A - 5A - 40 - 30 = 0

A² + 3A - 70 = 0

By Using Quadratic Formula We Get,

A = [ -3 ± √9 + 280 ] / 2

A = [ -3 ± 17 ] /2

A = [-3 + 17] / 2   or   A = [-3 - 17] / 2

A = 7    or   A = -10

A ≠ -10 (Because Age Cannot be Negative)

Hence, A = 7

Answer 2

Answer:

Step-by-step explanation:

Let Rena's present age be x.

Rena's age 5 years ago = x-5

Rena's age 8 years later = x+8

(x-5) × (x+8) =30

x^2+3x-40=30

x^2+3x=70

x^2+3x-70=0

x^2+10x-7x-70=0

x(x-10)-7(x-10)=0

(x-10)(x-7)=0

x-10=0

x=10

(10-5)×(10+8)

=5×18

=90

Therefore, x will be 7 and not 10