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Question

Which of the following statements is correct?

I. If x = 12, y = –2 and z = –10, then x³ + y³

+ z³ = 720

II. If x + y = 48 and 4xy = 124, then 4x² +4y² = 9368

A Only I Correct Answer Incorrect Answer
B Only II Correct Answer Incorrect Answer
C Neither I nor II Correct Answer Incorrect Answer
D Both I and II Correct Answer Incorrect Answer
E none of these Correct Answer Incorrect Answer

Solution

For statement first – X =12, y=-2 and z= -10 x+ y+ z =12 -2-10=0 x +y + z=0 so. x³ + y³+ z³ = 3xyz = 3 ×12 × -2× -10 = 720 For statement second – x + y = 48, 4xy = 124 4x² +4y² = 4480 4(x² +y²) = 4480 4(x² +y²) = 4[ (x+ y) ²-2xy] =4[(48) ² -2×31] =4[2404-62] =4 ×2342=9368,

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