Test 4 Sample Math 123a

Solve the following system a. by substitution b. by elimination x = 6 + y x – y = 6 x + 2y = - 3 x + 2y = -3Solve the following systems by any methodA. x + y = 6 B. y = 4 + x C. 3x – 2y = 3 x – y = 2 x + 2y = 6 4x – 3y = -1Simplify 1. 3x + 7(2x – 5) 2. 3(x + 7) – 2(3 – 4x)

3. 3x(4x2 – 2x + 1) – 4x2(5 – 3x) 4. 2x(xy – x) + x2(3 – 5y)

5. (3x + 7)(2x – 5) 6. (2x + 5)(x – 2) + (x – 1)(3x + 2 )

7. (3x – 5 ) 2 8. (4x – 5)(4x + 5)

9. (2x –3)(x + 1) – (4x – 3)(x – 1) 10. (2x + 3)(x – 3) – (2x – 3)2

11. a. Evaluate –2x2y – 3xy2 if y = –2. b. Evaluate –2x2y – 3xy2 at (3, –2).

12. Let x = price / lb of peanuts, y = price / lb for cashews. Find x and y given the following invoice.

Order 1. (in lb) Order 2 (in lb)

Cashews 2 3

Peanuts 3 1

Cost $16 $16

13. Peanuts costs $2/lb, cashews costs $8/lb. How many lbs of each are needed to get 50 lbs of peanut–cashews–mixture that cost $3/lb? Write down what x and y represent and make a table.

14. We have $8,000 in two accounts, one at 8% and the other at 6%. Their combined interest is $600. How much is in each account?

15. A. Calculate and leave the answer B. Calculate and leave the answer as a reduced fraction 40 * 3 – 3 * 2 2 as a reduced fraction 40 * 3-1 – 3 * 2 -2 16. A. Write the number 2,340,000,000 in B. Convert 3.76 x 10 -5 into a decimal the scientific notation

C. compute 2.3x1060 x 8.9 x10-38 and put the answer in the scientific notation

17. Simplify and leave the answer in positive exponent:

B .x2 y−4

x−5 y2A .

21x2 y4

14 x5 y2