Help x-intercept 2

Help x-intercept 2

Postby Guest » Sat Jan 12, 2019 7:52 pm

2. Which of the following parabolas opens upward and appears narrower than y=−3x 2 +2x−1 ?
o A. y= 4x^2 −2x−1
o B. y= − 4x^2 +2x−1
o C. y= x^2 +4x
o D. y= − 2x^ 2 +x+3

Answer:
A

CORRECT OR NOT

3. Which of the following parabolas is 2 units higher than y=2x 2 −4x−1 , but has the same shape and opens in the same direction?
o A. y=2x 2 −6x−1
o B. y=2x 2 −2x−1
o C. y=2x 2 −4x−3
o D. y=2x 2 −4x+1

Answer
D

CORRECT OR NOT


4. What are the coordinates of the vertex of the parabola y=x 2 +2x−1 ?
o A. (−2,5)
o B. (−1,−2) ………
o C. (−2,−1)
o D. (−1,2)

Answer
B

CORRECT OR NOT


5. Which of the following equations has an axis of symmetry with the equation x=1.5 ?
o A. y=2x 2 −6x−1
o B. y=2x 2 −3x+1
o C. y=x 2 +6x−3
o D. y=2x 2 +3x+2

Answer
A

CORRECT OR NOT

THANKS MUCH
Guest
 

Re: Help x-intercept 2

Postby Guest » Thu May 16, 2019 5:14 pm

You really shouldn't feel the need to ask! Have confidence in yourself.

In (2) you should immediately see the "-" coefficient of [tex]x^2[/tex] on B and D so those open downwards. The coefficient on (A) is 4 while the coefficient on (C) is 1. Each point on (A) will be 4 times as high as (C). Yes, (A) is the correct answer.

In (3) to have the same "shape" the coefficients of [tex]x^2[/tex] and [tex]x[/tex] must be the same so that eliminates (A) and (B). Of (C) and (D), 1= -1+ 2 so, yes, (D) is correct.

In (4) complete the square! [tex]x^2+ 2x- 1= x^2+ 2x+ 1- 2= (x+ 1)^2- 2[/tex]. Since a square is never negative the smallest possible value of [tex](x+ 1)^2[/tex] is 0, when x= -1 and then [tex](x+ 1)^2- 2= 0- 2= -2[/tex]. Yes, (B), (-1, -2), is correct.

For 5, any quadratic that has x= 1.5 as axis of symmetry must be of the form [tex]y= a(x- 1.5)^2+ b[/tex] for some numbers a and b. If a= 2 (as it would have to be for (A), (B), and (D)) [tex]2(x- 1.5)^2+ b= 2x^2- 2(3)x+ 4.5+ b= 2x^2- 6x+ (4.5+ b)[/tex]. Yes, that looks like (A). (For (C), we would have to have [tex](x- 1.5)^2+ b= x^2+ 3x+ 2.25+ b[/tex] but the coefficient of x is wrong.
Guest
 


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