Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

If $x + y + z = 17, xyz = 171$ and $xy + yz + 2zx = 111$,then the value of $\sqrt[3]{(x^{3}+y^{3}+z^{3}+xyz)}$ is:

Options:

-64

4

0

-4

Correct Answer:

-4

Explanation:

x + y + z = 17

xy + yz + zx = 111

xyz = 171 

We know that,

(x + y + z)2 = x2 + y2 + z2 + 2(xy + yz + zx)

= 172 = x2 + y2 + z2 + 2 × 111

= x2 + y2 + z = 289 – 222

= x2 + y2 + z  = 67

We also know that,

x+ y3 + z3 – 3xyz = (x + y + z)[x2 + y2 + z2​ – (xy + yz + zx)]

= x+ y3 + z3  – 3 × 171 = 17 × (67 – 111)

= x+ y3 + z3  – 513 = -748

= x+ y3 + z3  = -748 + 513

= x+ y3 + z3  = -235

$\sqrt[3]{(x^{3}+y^{3}+z^{3}+xyz)}$ = $\sqrt[3]{-235 +171)}$ = -4