Algebra Skills test answers

[1] State the degree of the polynomial: x3 - x2 + x4

degree is 4, due to last term

[2] Remove parentheses and combine like terms: -4m2 + 3n2 - 5n - [3m2 - 5n2 + 2n - (3m2 - 4n2)]

= -4m2 + 3n2 - 5n - [3m2 -5n2 + 2n - 3m2 + 4n2] : red terms cancel

= -4m2 + 3n2 - 5n + 5n2 - 2n - 4n2 = -4m2 + 4n2 - 7n

[3] Factor out the largest common factor: 9x2y2z4 - 18x3y2z

= 9x2y2z(z3 - 2x)

[4] Factor out the largest common factor, and then combine like terms: 4(3-x)2 - (3-x)3 + 3(3-x)

= (3 - x)[4(3 - x) - (3 - x)2 + 3] = (3 - x)(6 + 2x - x2)

 

[5] Factor: 27x3 - 64y3

= (3x)3 - (4y)3 = (3x - 4y)[(3x)2 + (3x)(4y) + (4y)2]

 

[6] Factor, i.e., write as A times B for some A & B: (m-p)2 + 4(m-p) + 4

= (m - p + 2) (m - p + 2)

 

[7] Simplify by writing as one term (it is 3 terms, now): 3 - -

= 3 - 2 - 6 = -5

 

[8] Solve for x: - = 1 : square both sides to get

()2 - 2. + ()2 = 12

(x + 2) - 2. + (x - 3) = 1

2x - 2 = 2.

x - 1 = . : now square both sides again to get

x2 - 2x + 1 = (x + 2)(x - 3) = x2 -x - 6 : the red terms cancel

-2x + 1 = -x - 6

x = 7

[9] Find all values of x for which 10x2 + x - 21 = 0

    Two possible methods:
    [A] Use quadratic formula with a=10, b=1, and c=-21, to get x =
-1 ± [12 - 4(10)(-21)]½
2(10)
    [B] Factor the given left side, to get (2x + 3)(5x - 7) = 0,
     In either above case, we find either x = -3/2 , or x = +7/5

 

[10] Solve for x: log(4x) = log(2) + log(x-3): combine right side as

log(4x) = log(2)(x-3) so that 4x = 2(x-3) and x = -3

A couple of students correctly noticed that x = -3 will make numbers in the original equation into complex numbers, and in some algebra courses, such situations are interpreted as if there were no solution (actually, no "real" solution)

     
This page last
updated 20 January 99