Will mark solve the system of equations. x2 = y + x + 8 y = -x + 2 a) ( radical 10 , 2 - radical 10 ) and ( radical 10 , 2 + radical 10 ) b) ( radical 10 , 2 - radical 10 ) and (- radical 10 , 2 - radical 10 ) c) ( radical 10 , 2 - radical 10 ) and (- radical 10 , 2 + radical 10 ) d) ( radical 10 , -2 - radical 10 ) and (- radical 10 , 2 + radical 10 )

Given: ab ≅ cd and ad ≅ bc prove: abcd is a parallelogram. statements reasons 1. ab ≅ cd; ad ≅ bc 1. given 2. ac ≅ ac 2. reflexive property 3. △adc ≅ △cba 3. ? 4. ∠dac ≅ ∠bca; ∠acd ≅ ∠cab 4. cpctc 5. ∠dac and ∠bca are alt. int. ∠s; ∠acd and ∠cab are alt. int. ∠s 5. definition of alternate interior angles 6. ab ∥ cd; ad ∥ bc 6. converse of the alternate interior angles theorem 7. abcd is a parallelogram 7. definition of parallelogram what is the missing reason in step 3? triangle angle sum theorem sas congruency theorem sss congruency theorem cpctc