hp40g+.book Page 5 Friday, December 9, 2005 1:03 AM

Example 4

Press to select the entire equation, then press

to reduce it to

9x2 – 6x – 80 .

Press , select

FACTOR, press and

then . The result is as shown at the right.

Now press , select

SOLVEVX, press and

press . The result is shown at the right.

Press to display CAS history, select D or a

version of it, and press .

Press , select SUBST,

press and, then complete the second argument: x = –5

Press to select the entire expression and

then to obtain the intermediate result shown.

Press once more to yield the result:175 . Therefore, D = 175 when

x= –5 .

A baker produces two assortments of biscuits and macaroons. A packet of the first assortment contains 17 biscuits and 20 macaroons. A packet of the second assortment contains 10 biscuits and 25 macaroons. Both packets cost 90 cents.

Calculate the price of one biscuit, and the price of one macaroon.

Solution: Let x be the price of one biscuit, and y the price of one macaroon. The problem is to solve:

Step-by-Step Examples

16-5