0,9:1=0,9
1:8=0,125
0,9+0,125=1,025
1) (a-3)(3a+1)-(2a+3)(4a-1)=3a^2+a-9a-3-(8a^2-2a+12a-3)=3a^2+a-9a-3-(8a^2+10a-3)=3a^2+a-9a-3-8a^2-10a+3=-5a^2-18a
2) (x+4)²-(x-2)(x+2)=x^2+8x+16-(x^2-4)=x^2+8x+16-x^2+4=8x+20
(-0,7)*(-10)^4-5*(-10)^3-32=-0.7*(10000)-5*(-1000)-32=-7000+5000-32=-2032