Answer:
Option B
Explanation:
Given that,
x+y+z=4, x-y+z=2 and x+2y+2z=1
△= [1111−11122]=1(−2−2)−1(2−1)+(2+1)]
= -4-1+3=2
△1=[4111−11122]=4(−2−2)−1(4−1)+1(4+1)
=4(−4)−3+5=−16−3+5=−14
△2=[141121112]
△2=1(4−1)−4(2−1)+1(1−2)=3−4−1=2
△3=[1141−12121]
△3= 1(-1-4)-1(1-2)+4(2+1)=(-5)+1+12=8$
x=△1△=−142=7, y=△2△=−2−2=1
and z=△3△=−82=−4
So, a=7, b=1, c=-4
Now, ab+bc+ca
= 7(1)+1(−4)+(−4)(7)=7−4−28=−25