91Ó°ÊÓ

Write a proof for exercise 8 in two-column form.

Name the definition or state the theorem that justifies the statement about the diagram.

If $\stackrel{↔}{RS}âŠ\yen \stackrel{↔}{TV}$, then $m∠6=90$.

Solve each system of equations by the substitution method.

$3x+y=19$

$2x–5y=–10$

Describe your plan for proving the following. You don’t need to give all the details.

Given: $\stackrel{¯}{AC}âŠ\yen \stackrel{¯}{BC}$;∠3 is complementary to ∠1.

Prove: $∠3â‰\dots ∠2$

Name the definition, postulate or theorem that justifies the statement.

If $\stackrel{¯}{\mathrm{RS}}â‰\dots \stackrel{¯}{\mathrm{ST}}$, then S is the midpoint of $\stackrel{¯}{\mathrm{RT}}$.

In the diagram,$∠\mathit{A}\mathit{F}\mathit{B}$ is a right angle. Name the figures described.

Two congruent supplementary angles.

Solve each system of equations by the substitution method.

3x + y = 19

2x – 5y = –10