Indicate by T or F whether the equations below are equivalent to a linear equation. This time you need to get all answers correctly before receiving credit.
1. $x^2 -5x + 4 = x^2+6x-11$
2. $\frac{1}{x+3} = \frac{1}{2x-3}$
3. $x^2+1 = x-x^2$
4. $3x + 4 = 5x -4$

Hint: Study the definition and discussion of 'linear equation'.