If x = 7, y = 4, z = 9, then which of the following is TRUE?
I. x + y + z = 20
II. x - y + z = 13
III. x + y - z = 3
IV. -x + y - z = -12
A. I and II
B. III and IV
C. I and IV
D. I and III
- AOption (a)
A
- BOption (b)
D
- COption (c)
C
- DOption (d)
B
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Correct answer
C
Why this answer is correct
Given:
x = 7, y = 4, z = 9
Calculation:
I. x + y + z = 20
LHS,
x + y + z = 7 + 4 + 9
⇒ x + y + z = 20
LHS = RHS
II. x – y + z = 13
LHS,
x – y + z = 7 – 4 + 9
⇒ x – y + z = 12
LHS ≠ RHS
III. x + y – z = 3
LHS,
x + y – z = 7 + 4 – 9
⇒ x + y – z = 2
LHS ≠ RHS
IV. -x + y – z = -12
LHS,
-x + y – z = -7 + 4 – 9
⇒ -x + y – z = -12
LHS = RHS
∴ I and IV are TRUE.