Without actually calculating the cubes, find the value of 45^3 - 25^3 - 20^3
URGENT!!!!
Answers
Answered by
113
45³ - 25³ - 20³
Without actually calculating squares and cubes we do as:
a³ - b³ = (a+b)(a²+b²+ab)
(45-25)(45²+25²+45*25) - 20³
20 (45²+25²+45*25) - 20³
20 [ (45²+25²+45*25 - 20² ] now take 25² - 20² is like a²-b²
20 [ 45² + 45*25 + (25-20)(25+20) ]
20 [ 45 (45 + 25 + 5 ) ]
20 *45 * 75
Without actually calculating squares and cubes we do as:
a³ - b³ = (a+b)(a²+b²+ab)
(45-25)(45²+25²+45*25) - 20³
20 (45²+25²+45*25) - 20³
20 [ (45²+25²+45*25 - 20² ] now take 25² - 20² is like a²-b²
20 [ 45² + 45*25 + (25-20)(25+20) ]
20 [ 45 (45 + 25 + 5 ) ]
20 *45 * 75
Answered by
20
Answer:
a+b+c=0 then a^3+b^3+c^3=3abc
here 45+(-20)+(-25)=0
hence 45³-25³-20³ =3*45(-25)*(-20)= 67500
hope it helps
Step-by-step explanation:
Similar questions