What is 230,800,000 in scientific notation

Simplify 15(x - 4)(x -1)-3(x + 4)(x - 1) with steps

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)

Is the product of two rational numbers irrational or rational? first, make a hypothesis by multiplying two rational numbers. then, use variables such as x=a/b and y=c/d and the closure property of integers to prove your hypothesis.