Question

If a-b=1 and a3-b3 = 61, then the value of ab will be

A) -20 B) 20 C) 30 D) 60

Answer 1

Answer:

B

Step-by-step explanation:

a-b=1

a3-b3=61

let a=3 & b=2

(3)3-(2)3=27-8=19 is not equal to 61

let a=4 &b=3

(4)3-(3)3=64-9=53 is not equal to 61

let a=5 &b=4

(5)3-(4)3=125-64=61

so a=5 &b=4

ao AB=5*4=20

B.20 is answer