How do you factor the expression 12t^8-75t^412t875t4?

1 Answer
Oct 17, 2016

12t^8-75t^4 = 3t^4(2t^2-5)(2t^2+5)12t875t4=3t4(2t25)(2t2+5)

color(white)(12t^8-75t^4) = 3t^4(sqrt(2)t-sqrt(5))(sqrt(2)t+sqrt(5))(2t^2+5)12t875t4=3t4(2t5)(2t+5)(2t2+5)

Explanation:

color(white)()
Difference of squares

The difference of squares identity can be written:

a^2-b^2 = (a-b)(a+b)a2b2=(ab)(a+b)

We will use this a couple of times.

color(white)()
Factor bb(12t^8 - 75t^4)

First note that both terms are divisible by 3t^4, so separate that out as a factor first:

12t^8-75t^4 = 3t^4(4t^4-25)

color(white)(12t^8-75t^4) = 3t^4((2t^2)^2-5^2)

color(white)(12t^8-75t^4) = 3t^4(2t^2-5)(2t^2+5)

color(white)(12t^8-75t^4) = 3t^4((sqrt(2)t)^2-(sqrt(5))^2)(2t^2+5)

color(white)(12t^8-75t^4) = 3t^4(sqrt(2)t-sqrt(5))(sqrt(2)t+sqrt(5))(2t^2+5)

The remaining quadratic (2t^2+5) does not factor further with Real coefficients, since 2t^2+5 >= 5 > 0 for any Real value of t.