The life expectancy of a typical lightbulb is normally distributed with a mean of 4,000 hours and a standard deviation of 42 hours. what is the probability that a lightbulb will last between 3,875 and 4,055 hours?

a)0.8835
b)0.7825
c)0.9133
d)0.9035

This is so hard and it’s for a test

To diagonalize an nxn matrix a means to find an invertible matrix p and a diagonal matrix d such that a pdp d p ap or [1 3 dh epap 3 let a=-3 -5 -3 3 3 1 step 1: find the eigenvalues of matrix a "2's" step 2: find the corresponding eigenvectors of a step 3: createp from eigenvectors in step 2 step 4 create d with matching eigenvalues.

Def rotates 90 clockwise about point a to create d’ e’ f’. therefore, which equation must be true ?