What ratio of nacn to hcn is needed to prepare a ph 10. 30 buffer? (ka of hcn is 4. 9 × 10⁻¹⁰).

△cde maps to △stu with the transformations (x, y) arrowright (x − 2, y − 2) arrowright (3x, 3y) arrowright (x, −y). if cd = a + 1, de = 2a − 1, st = 2b + 3 and tu = b + 6, find the values of a and b. the value of a is and the value of b is .

Sam opened a money-market account that pays 3% simple interest. he started the account with $7,000 and made no further deposits. when he closed the account, he had earned $420 in interest. how long did he keep his account open?

If the angle bisectors of a pair of opposite angles of a quadrilateral are the opposite sides of a parallelogram formed by the two angle bisectors and two sides of the quadrilateral, is the quadrilateral always a parallelogram? explain your answer.