Hi guys, I have got some questions which i am unable to solve despite trying for so long. Would appreciate if someone would enlighten me

Differentiate the following:

1) y= a ²-x ² (My answer was 2a-2x but the given answer is -2x)

2)f(x)=x ²(4x-2) ( My answer was 24x ²-16x but given was 12x ²-4x)

3) x.√1+x²

Thank you in advance