Is negative plus negative equal to positive or negative?

Is negative plus negative equal to positive or negative?

Negative. Because both numbers are negative, the sum must be negative

270 channel fractional addition, subtraction, multiplication and division
270 channel fenshujiajianchengchusuanshi

The formula of derivative addition, subtraction, multiplication and division,
I can't find the book. I'm in a hurry

Addition and subtraction: y = u soil V, y '= u' soil V '
Multiplication and division: y = UV, y '= u'v + UV'
y=u/v,y'=(u'v-v'u)/v2

What is the order of decimal mixing and integer mixing?

From left to right, multiply and divide first, then add and subtract. If there are brackets, calculate those in brackets first