Ionly need one solved i just need to understand how to do it asap. me

#19= -11, #20=4, #21=2, #22= 2, #23= 1/3, #24= -3/5, #25= 1/2

Step-by-step explanation:

#19= 1-3x^2    What you do first is that you do 2^2 to get 4, than multiply i by 3 to get 12, than you subtract 12 from 1( 2^2=4, 4*3, 1-12= -11)

#20=2-3x+x^2     what you do is sub in #, 2-3(-1)+(-1)^2, 2+3-1= (2+3)-1, 5-1=4

#21=x-3x^2      What you do is sub #, -1-3(-1)^2=-1+3=2

#22=x+x^2    sub #, 1+1=2

#23= 1/x+1,     sub #, to get 1/2+1 =1/3

#24=x/2-x,    sub #, to get -3/ 2+3= -3/5

#25=1/squarert of x,  sqrt of 4 is 2, 1/2