Which is the best description of the equivalency of the two expressions?

They are equivalent expression because when x = 2, the expressions have the same value.

Step-by-step explanation:

Equivalent expressions are identified when the value of the variable can be substituted in each equation and the same result is found.  So, even though the expression may look different, when you put the same number in for the variable, you will get the same value.  You can also 'simplify' your expressions by combining like terms:

Expression 1:  5x² - 2x + 6x  - 4 + 3 = 5x² + 4x - 1

Expression 2:  6x² - x² - 6x + 10x + 6 - 7 = 5x² + 4x -1

Since both expressions are the same after simplifying, they will produce the same value when x = 2, so they are equivalent.  

step-by-step explanation:

∆abc has the points a(1, 7), b(-2, 2), and c(4, 2) as its vertices. formed with the point d(1, 2) as its third vertex, then ∆abd is triangle.

x + 4/7

step-by-step explanation:

use cymath