Answers

2015-10-05T12:32:47+05:30

This Is a Certified Answer

×
Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
2(0.3)³ + (0.4)³ + (0.5)³ + (-0.7)³ + (-0.8)³
= (0.3)³ + (0.3)³ + (0.4)³ + (0.5)³ + (-0.7)³ + (-0.8)³
= (0.3)³ + (0.4)³ + (-0.7)³ + (0.3)³ +  (0.5)³ + (-0.8)³
= [(0.3)³ + (0.4)³ + (-0.7)³] + [(0.3)³ +  (0.5)³ + (-0.8)³]  ------------------(1)

We know that if a+b+c=0, then a³+b³+c³ = 3abc

In [(0.3)³ + (0.4)³ + (-0.7)³]; 
0.3 + 0.4 + (-0.7) = 0.7 -0.7 = 0
So (0.3)³ + (0.4)³ + (-0.7)³
= 3×0.3×0.4×(-0.7) 
⇒ [(0.3)³ + (0.4)³ + (-0.7)³= -0.252       ------------------------------------(2)

Similarly In [(0.3)³ +  (0.5)³ + (-0.8)³]; 
0.3 + 0.5 + (-0.8) = 0.8 -0.8 = 0
So (0.3)³ + (0.4)³ + (-0.7)³ 
= 3×0.3×0.5×(-0.8) 
⇒ [(0.3)³ +  (0.5)³ + (-0.8)³= -0.360       ------------------------------------(3)

So putting equation (2) and (3) in equation (1)
[(0.3)³ + (0.4)³ + (-0.7)³] + [(0.3)³ +  (0.5)³ + (-0.8)³
= (-0.252) + (-0.360)
= -0.612

So 2(0.3)³ + (0.4)³ + (0.5)³ + (-0.7)³ + (-0.8)³ = -0.612
3 4 3
2015-10-05T16:06:41+05:30

This Is a Certified Answer

×
Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
 we use the Algebra formula : a³ + b³ + c³ = 3 a b c    if a+b+c =0
  we observe that  0.3 + 0.4 + (-0.7) = 0
                 and ,  0.3 + 0.5 + (-0.8) = 0

LHS = 0.3³ + 0.4³ + (-0.7)³ + 0.3³ + 0.5³ + (-0.8)³
       = 3 * 0.3 * 0.4 * (0.7)  +  3 * 0.3 * 0.5 * (-0.8)
       =  - 0.9 * (0.28 + 0.40)
       = - 0.612

2 5 2