Advertisements
Advertisements
Question
If a – b = 3 and ab = 10, find : a3 – b3.
Sum
Advertisements
Solution
a − b = 3
⇒ (a − b)3 = (3)3
⇒ a3 − b3 − 3ab (a − b) = 27
⇒ a3 − b3 − 3×10 (3) = 27
⇒ a3 − b3 − 90 = 27
⇒ a3 − b3 = 27 + 90
⇒ a3 − b3 = 117
Alternative Method :
(a − b)3 = a3 − b3 − 3ab (a − b)
⇒ (3)3 = a3 − b3 − 3×10 (3)
⇒ 27 = a3 − b3 − 90
⇒ 27 + 90 = a3 − b3
⇒ 117 = a3 − b3
⇒ a3 − b3 = 117
shaalaa.com
Application of Formulae
Is there an error in this question or solution?
APPEARS IN
RELATED QUESTIONS
If a+b=5 and ab = 6, find a2 + b2
If a2 + b2 = 29 and ab = 10, find : a − b
If a2 + b2= 10 and ab = 3; find : a – b
If a2 + b2= 10 and ab = 3; find : a + b
If `"a" + 1/"a"=3`, find `"a"^2+1/"a"^2`
If a + b = 6 and ab = 8, find: a3 + b3.
Find:
`a^3-1/a^3`, if `a -1/a = 4`.
If `3"x"+1/(3"x")=3`, find : `9"x"^2+1/(9"x"^2)`
If `3"x"+1/(3"x")=3`, find : `27"x"^3+1/(27"x"^3)`
If 3x + 2y = 9 and xy = 3, find : 27x3 + 8y3.
