William has scored a total of 235 points on the first three math tests taken in his mathematics class. If his mathematics test are always worth 100 points, how many points must he earn on his next test in order to have an average of 80%

85 points

Step-by-step explanation:

His total points will be 235+x

Number of tests will be 4

(235+x)/4 = 80

multiply by 4

235+x= 4*80

235+x= 320

x=320-235

x= 85

He has to get 85 points to average 80

x= -3 and

step-by-step explanation:

to find the roots of a cubic, use division or factoring to find the factors then set equal to 0. as this is a difference of cubes, it factors into

where a is the cube root of .

here   this is 27 and the cube root of 27 is 3. so we write using the form:

.

set each factor to 0 and solve for x.

x-3=0

x=3

the quadratic expression does not factor and must be solved using the quadratic formula.

where a = 1, b=3, and c=9

this cubic has two complex roots.