(i) Let x = -12, y = 7 and z = 5We observed that,x + y + z = -12 + 7 + 5 = 0We know that if,x + y + z = 0Then,x3 + y3 + z3 = 3xyz(-12)3 + (7)3 + (5)3 = 3 (-12) (7) (5)= -1260(ii) Let x = 28, y = -15 and z = -13We observed that,x + y + z = 28 – 15 – 13 = 0We know that if,x + y + z = 0Then,x3 + y3 + z3 = 3xyz(28)3 + (-15)3 + (-13)3 = 3 (28) (-15) (-13)= 16380

Q. 144.3( 189 Votes )

Without actually

Class 9th NCERT - Mathematics 2. Polynomials

Answer :

(i) Let x = -12, y = 7 and z = 5

We observed that,

x + y + z = -12 + 7 + 5 = 0

We know that if,

x + y + z = 0

Then,

x³ + y³ + z³ = 3xyz

(-12)³ + (7)³ + (5)³ = 3 (-12) (7) (5)

= -1260

(ii) Let x = 28, y = -15 and z = -13

We observed that,

x + y + z = 28 – 15 – 13 = 0

We know that if,

x + y + z = 0

Then,

x³ + y³ + z³ = 3xyz

(28)³ + (-15)³ + (-13)³ = 3 (28) (-15) (-13)

= 16380

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