The polynomial equation x(x2+4)(x2-x-6)=0 has how many real roots?

Solution:

x2+4 contributes complex zeros. This means that the factors x and x2-x-6 contribute real zeros. Therefore the polynomial has 3 real zeros

The average of 9 consecutive numbers is 20 the greatest of these numbers is ?

x+(x+1)+...+(x+8)=9x+36

so if they average to 20 we can say:

(9x+36)/9=20

simplifying...

x+4=20,

so x=16

the greatest of the 9 numbers must be 24

The mean of 50 observations was 160. It was detected on rechecking that the value 175 was wrongly copied as 75 for the computation of the mean. Find the correct mean.

x=(160*50+100)/50=162

If my math final is worth 10% of my grade and I have a 90 in the class, what do I need to get on the test to maintain an A in the class?

0.1*x+0.9*90 > 90
0.1*x > 90-81
x > 90

if average of 10 numbers is zero.If 72 and 12 are added to the list,find the new average

ave=(0+72+12)/(10+2)=7

A student scores 75 and 91 on two different tests of 100 points. If the maximum score on the next test is also 100 points, what score does the student need to maintain an average of at least 80?

 

Joe scored 85, 89, 86, and 93 on the first 4 tests in math. what must he score to average 90

if you mean that he will take one more test, and all the tests have the same weight then...
(85+89+86+93+x)/5=90
x+353=450
x= 97