Look below for problem

Step-by-step explanation:

(3x^2 + 2x) + (-x +  9)             Remove the brackets

3x^2 + 2x - x + 9                    Watch out for the sign in front of the x

3x^2 + x +    9                         No more reduction can take place.

(-2x^2 + 5x - 7) + (3x + 7)       Remove the brackets

-2x^2 + 5x - 7 + 3x + 7

-2x^2 + 5x + 3x - 7 + 7           Combine

-2x^2 + 8x                              The 7s cancel -- they are of opposite signs.

No more reduction can take place. The powers on the variables have to be equal before any cancelation can take place.

hope it you

step-by-step explanation:

sin(7pi/6 - pi/3)  

= sin(7pi/6 - 2pi/6)  

= sin(5pi/6)  

= sin(pi - pi/6)  

= sin(pi/6)  

= 1/2  

sin 7pi/6 - sin pi/3  

= sin (pi + pi/6) - sin pi/3  

= -sin pi/6 - sin pi/3  

= -1/2 - sqrt(3)/2  

= -(1+sqrt(3))2