5t-10t^2÷5t

if you wanted to simplify, we would get 5t--2t = 5t+2t = 7t

Taking into account the usual carelessness with parentheses, if you meant

(5t-10t^2)/5t, then you would have 1-2t

Otherwise, keeping track of the signs, you'd have 5t-2t = 3t

I'll go with Steve's answer

the other one mystifies me.

To simplify the expression 5t - 10t^2 ÷ 5t, we need to follow the order of operations (PEMDAS/BODMAS) and apply the rules for combining like terms.

Step 1: Simplify the division: 10t^2 ÷ 5t
When dividing like terms with the same base (t), we subtract the exponents. So, 10t^2 ÷ 5t simplifies to 2t^(2-1) = 2t.

Now, the expression becomes: 5t - 2t.

Step 2: Combine like terms: 5t - 2t
When subtracting or adding like terms, we simply combine the coefficients (the numbers in front of the variable). In this case, 5t and -2t are like terms because they have the same variable (t).

Combining the coefficients, we get: 5t - 2t = 3t.

Therefore, the simplified expression is 3t.