– WELCOME TO AN APPLICATION
OF POLYNOMIAL EQUATIONS. THE POLYNOMIAL EQUATION GIVEN
HERE DESCRIBES THAT BILLIONS OF FLU VIRUS
PARTICLES, Y, IN A PERSON’S BODY X DAYS AFTER
BEING INFECTED. WE WANT TO FIND THE NUMBER
OF VIRUS PARTICLES IN BILLIONS AFTER THREE DAYS
OF BEING INFECTED. SO WE WANT TO FIND THE VALUE OF
Y WHEN X, THE NUMBER OF DAYS,
IS EQUAL TO 3. SO IF WE SUBSTITUTE 3 FOR X WE
WOULD HAVE Y=-0.72 AND THEN 3 TO THE FOURTH POWER, IF WE SUBSTITUTE FOR 3 FOR X,
PLUS 3 x 3 TO THE THIRD POWER. AGAIN, SUBSTITUTING 3 FOR X,
AND THEN + 28.2. AND I WANT TO SIMPLIFY
THE RIGHT SIDE USING THE ORDER OF OPERATIONS, WHICH MEANS WE SHOULD SIMPLIFY
THE EXPONENTS FIRST. WELL 3 TO THE FOURTH=3 x 3 x 3
x 3 OR 4 FACTORS OF THREE, WHICH=81. SO WE -0.72 x 81 + 3 x 3 TO THE
THIRD WOULD BE 3 x 3 x 3, OR 3 FACTORS OF 3, WHICH IS 27 AND THEN + 28.2. NEXT WE WOULD MULTIPLY
AND THEN ADD AND SUBTRACT FROM LEFT TO RIGHT. SO FOR THE NEXT STEP WE’LL FIND
THIS PRODUCT AND THIS PRODUCT AND THEN FIND THE SUM. SO WE HAVE -0.72 x 81=-58.32. AND THEN WE HAVE 3 x 27=81. LET’S JUST GO AHEAD
AND CHECK THAT. SO AGAIN,
WE HAVE -58.32 + 81 + 28.2.   AND NOW
WE’LL ADD FROM LEFT TO RIGHT.   SO Y=50.88, WHICH MEANS 50.88
BILLION VIRUS PARTICLES ARE PRESENT AFTER
THREE DAYS OF BEING INFECTED.   NOW I DO WANT TO POINT OUT THAT WE DID FIND THE VALUE
OF Y CORRECTLY USING THE ORDER OF OPERATIONS, BUT WITH MOST CALCULATORS
WE COULD HAVE JUST TYPED IN THE RIGHT SIDE OF THE FIRST
EQUATION HERE TO DETERMINE THE VALUE OF Y. SO I DO ALSO WANT TO SHOW THAT. WE WOULD JUST TYPE IN -0.72 x 3
RAISED TO THE FOURTH POWER, HERE’S THE EXPONENT KEY,
+ 3 (3 TO THE THIRD). SO 3 EXPONENT 3 AND THEN + 28.2
AND ENTER. AS WE CAN SEE, THE ANSWER
IS THE SAME. I HOPE YOU FOUND THIS HELPFUL.