Please help me with this! +19 points!

Simplify (a/b - b/a) times (a - a^2/a+b) a - a^2/a=b is a mixed number

Which math sentence can be used to determine if the triangle is a right triangle?

The average human heart beats 1.15 \cdot 10^51.15⋅10 5 1, point, 15, dot, 10, start superscript, 5, end superscript times per day. there are 3.65 \cdot 10^23.65⋅10 2 3, point, 65, dot, 10, start superscript, 2, end superscript days in one year.how many times does the heart beat in one year? write your answer in scientific notation, and round to one decimal place.