Plzz help
What is the solution of the quadratic inequality x^(2)-4x-32≥0 plz help would the answer be (-4,8)?

Question

Plzz help
What is the solution of the quadratic inequality x^(2)-4x-32≥0  plz help would the answer be (-4,8)?

anonymous · Answer

if not what am i doing wrong?

anonymous · Answer

-4 & 8 are solutions for the equality

anonymous · Answer

so would it be (infinity,-4), (8.infinity)

anonymous · Answer

im confused :/ i always get this question wrong

danmac0710 · Answer

So factorise the quadratic part into 2 linear factors or brackets. You should get (x-8)(x+4).... you should always check to see that this process this expands to give you the quadratic you started with. Then imagine the graph or better still draw it, of the quadratic. This one will be a smiley rather than a valley shaped curve (opening upwards!) and will cross the x-axis at -4 and +8 as your linear factors will then be equal to zero. The region of the curve which is above the x-axis (where it is greater than y=0) is when x is less than -4 and greater than +8.... you then need to look at the question and see if it was exactly greater than 0  whether y values can be also equal to zero. In your case they can so the complete solution set of x-values is: 
−4≤x∪x≥8

anonymous · Answer

the answer choices tell me         (-4,8)                 is this correct?

danmac0710 · Answer

I hope this helps. You really need to know how to factorise quadratics, and sketch them, and use inequality notation... quite a lot to learn to do this question confidently. Good luck!

anonymous · Answer

this helped by the way thanks but i don't know why this isn't in the answer choices

anonymous · Answer

do i have to simplify it?

danmac0710 · Answer

The way you wrote the answer (-4,9) looks to me like a point's coordinates. If using the bracket style of inequality notation I would personally write it like this: hang on I canot remember. I will have a quick revision session and tell you in 1 minute

anonymous · Answer

These are the answer choices
A. (infinity,-4) U (8,infinity)
B. (infinity,-4] U [8,infinity)
C. (-4,8)
D. [-4,infinity)

anonymous · Answer

|dw:1360976708170:dw|. Here is a way you can solve an inequation ($$ax ^{2}+bx+c \le q$$). You first solve, the equation ax^2+bx+c=0. Then you draw the graph and place the zeros of the equation. Between the zeros you put the contrary sign of a and besides the sign of a. You then see easily the solutions of the inequation

danmac0710 · Answer

It is B definitely. I just was not used to their notation. You should check this page out, it's really good: http://www.mathsisfun.com/sets/intervals.html They always help me when I am stuck on that website. It has good clear explanations. Good luck.