Question Details

Given three real numbers x, y, and z such that x2+y2+z2=250 and xy+yz-zx=65, determine the value of (x-y+z)2.

Options

A

120

B

130

C

185

D

380

Show Answer

Correct Answer :

Option A

120

92

Solution :

The correct answer is 120.

To find the value of (x-y+z)2, we can use the algebraic expansion for the square of a trinomial:

(a+b+c)2=a2+b2+c2+2ab+2bc+2ca

Substituting a=x, b=-y, and c=z into the expansion formula:

(x-y+z)2=x2+(-y)2+z2+2(x)(-y)+2(-y)(z)+2(z)(x)

Simplifying each term gives:

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

By factoring out -2 from the last three terms, we can regroup the expression as:

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

We are given the values of the expressions in the parentheses:

x2+y2+z2=250

xy+yz-zx=65

Substituting these values into our simplified expression:

(x-y+z)2=250-2(65)

(x-y+z)2=250-130=120

Thus, the value of (x-y+z)2 is 120.

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