Rational algebraic expressions

For which value of x is the expression (x + 1) / (x + 6) undefined?

Simplify: (x² − 1) / (x − 1)

Simplify: ($5x^{2}$/2) $\times$ (6/x)

Simplify: (7x/4) $\div$ (x/4)

Simplify: (x² − 6x + 8) / (x − 4)

Simplify: ($3x^{2}$/2) $\times$ (6/x)

For which value of x is the expression (x − 4) / (x − 1) undefined?

Simplify: (x² + x − 20) / (x + 5)

Solve for x (x ≠ 0): 20/$x=4$

Simplify: ($3x^{2}$/5) $\times$ (20/x)

Simplify: 4/$x+8$/x

Simplify: (x² − x − 2) / (x + 1)