Michael J. answered 07/27/15
Tutor
5
(5)
Effective High School STEM Tutor & CUNY Math Peer Leader
12)
2x - 3y + z = -1 eq1
2x - 2y - 2z = -8 eq2
x + 5y - 3z = 2 eq3
2x - 2y - 2z = -8 eq2
x + 5y - 3z = 2 eq3
We have 3 equations with three variables. We need to use a combination of substation method and elimination. Let's substitute one equation into 2 other equations to reduce the number equations and variables.
Substitute eq1 into eq2 and eq3.
From eq1,
z = -2x + 3y - 1
2x - 2y - 2(-2x + 3y - 1) = -8
2x - 2y + 4x - 6y + 2 = -8
6x - 8y = -10 new eq2
x + 5y - 3(-2x + 3y - 1) = 2
x + 5y + 6x - 9y + 3 = 2
7x - 4y = -1 new eq3
These are the new equations we will work with.
6x - 8y = -10 new eq2
7x - 4y = -1 new eq3
Multiply new eq3 by 2. Keep new eq2.
6x - 8y = -10 new eq2
14 - 8y = -2 new eq3
Subtract new eq3 from new eq2 to eliminate the y terms.
-8x = -8
x = 1
Substitute this value of x into new eq2 to solve for y.
6(1) - 8y = -10
6 - 8y = -10
-8y = -16
y = 2
We can solve for z, but that is not necessary. If we look at our answer choices, each solution set in written in the form (x y, z).
So far, our solution is (1, 2, z). The only answer choice that matches this pair is choice (C).
13)
We can write a system of equations to represent the situation.
Let x = time in hours
Let y = distance
For the bus
y = 50x + 210 eq1
For the van
y = 60x + 170 eq2
Since both vehicles need to be at the same distance, we equate both of them.
50x + 210 = 60x + 170
Solve for x.
Subtract 50x on both sides of the equation.
210 = 10x + 170
Subtract 170 on both sides of the equation.
40 = 10x
Divide 10 on both sides of the equation.
4 = x
Your answer is (B).
14)
Solve for y in each equality.
4x + 3y < 12 -----> 3y < -4x + 12 -----> y < (-3/4)x + 4
2x - 5y > 10 -----> -5y > -2x + 10 -----> y > (2/5)x - 2
Now we just look for the point that lies below the line y=(-3/4)x + 4 , and at the same time above the line y=(2/5)x - 2.
15) This is same as the previous question. Draw a coordinate system and draw lines on that coordinate system based on the restrictions.
Pick the answer that satisfies all of those restrictions.
16)
The degree of a polynomial is the highest value of the exponent in the polynomial. The highest exponent is 5 because of the term 2h5.
The degree is 5.
17)
(7a2 - 11a - 9) + (13a2 + 21a - 3)
Distribute the terms to get rid of parentheses.
7a2 - 11a - 9 + 13a2 + 21a - 3
Combine like terms and get your answer.
18)
The fastest way to do this is to multiply the term outside the parenthesis by the first term inside the parenthesis.
(2c3)(3c3) = 6c6
This is the first term in the polynomial. The answer choice that has this first term is choice (D).
19)
(x - 4)(x2 + 3x - 1)
Use (x2 + 3x - 1) as the GCF.
x(x2 + 3x - 1) - 4(x2 + 3x - 1)
Now distribute and combine like terms to get your answer.
20)
9x2 - 4
This is difference of perfect squares. This is because 32 is 9, x*x is x2, and 22 is 4.
(3x + 2)(3x - 2)
21)
3ab - 6a + 4b - 8
To factor, we group each part.
3a(b - 2) + 4(b - 2)
Notice that (b - 2) is the GCF here.
(b - 2)(3a + 4)
Since the question only asks for a single factor, pick the one from the answer choice that match the work done here.
And we are done here! :)