Hint:
(13+15)^3 = 13^3 + 3*13^2*15 + 3*13*15^2 + 15^3
Without actual calculating the cube the value of (28)^3 +(-15)^3 +(-13)^3 is
(a) 16380
(b)-16380
(c)15380
(d)-15380
2 answers
using a^3- b^3 = (a-b)(a^2 + ab + b^2)
(28)^3 +(-15)^3 +(-13)^3
= (28 - 15)(28^2 + 28(15) + 15^2) - 13^3
= 13[ 28^2 + 28(15) + 15^2 - 13^2]
= don't know how to avoid doing an actual calculation
(28)^3 +(-15)^3 +(-13)^3
= (28 - 15)(28^2 + 28(15) + 15^2) - 13^3
= 13[ 28^2 + 28(15) + 15^2 - 13^2]
= don't know how to avoid doing an actual calculation
1 answer