a3 +3ab(a + b) + b3 is equal to…….
a) (a – b)3
b) (a + b)3
c) a3 + b3
d) a3 – b3
a3 – 3ab(a – b) – b3 is equal to…….
a) (a – b)3
b) (a + b)3
c) a3 + b3
d) a3 – b3
(a + b)2 – (a – b)2 is equal to…….
a) 2ab
b) a2 – b2
c) 4ab
d) a2 + b2
Explanation:(a + b)2 – (a – b)2
(a2 + b2 +2ab) – (a2 + b2 –2ab)a2 + b2+2ab – a2+ b2 + 2ab = 4ab
Find the value of a3 + b3, when a+b=4, and ab=5
a) 4
b) 20
c) 64
d) 320
Explanation:a + b=4
(a+b)3=(4)3
a3 + b3+3ab(a + b) = 64 putting the values
a3 + b3 + 3(5)(4) = 64
a3 + b3+ 60 =64 a3 + b3=64 – 60
a3 + b3=4
Find the value of a3 + b3, when a+b=3, and ab=20
a) 4
b) - 4
c)- 153
d) 340
Explanation:a + b= 3
(a+b)3=(3)3
a3 + b3+3ab(a + b) = 27putting the values
a3 + b3 + 3(20)(3) = 27
a3 + b3+ 180 =27 a3 + b3= 27 – 180
a3 + b3= – 153
Find the value of a3– b3, when a – b=2, and ab= 15
a) 98
b) - 98
c) 150
d) 30
Explanation:a + b= 3
(a–b)3=(2)3
a3– b3– 3ab(a – b) = 8 putting the values
a3– b3 – 3(15)(2) = 8
a3– b3– 90 = 8 a3– b3= 8 + 90
a3– b3= 98
