What is the intersection of the three sets: a = {1, 2, 3, 4, 5}, b = {1, 2, 3, 6, 8}, and c = {2, 3, 4, 6, 7}? a. {1, 6, 8} b. {1, 2, 3, 4, 5, 6, 7, 8} c. {3, 4, 5} d. {2, 3}

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)

If x-1 and x+3 are the factors of x3+10x2+ax+b find a and b

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?