Which cannot be used in a proof?
a. theorems
b. postulates
c. properties
d. undefined terms

D.Undefined Terms

Step-by-step explanation:

The reason in a mathematical proof can be a given information, vocabulary definitions, properties, postulates or previously proved theorems.

But the undefined terms are the terms which used in geometry to define other terms.

Therefore , the undefined terms cannot be used in a mathematical proof .

Hence , D is the correct option.

the answer is y < -3 or   y > 3

-3y > 7 + 2

-3 y > 9

y < -3

y < -3

step-by-step explanation:

-3y - 2 > 7

-3y -2 + 2 > 7+2

-3y > 9

-3y/-3 < 9/-3   (change the inequality sign when multiplying or dividing by a negative number)

y < -3