Sagot :
1) d=√(8²+5²+3²)=√98=7√2
2) 12a²-36a+27/9-4a² =8a²-36a+3
4a²+12a+9/12a+18 = 4a²+51/4a+18
3) x²-y²/x²+xy : x²y-xy²/x²(x+y) = (x^4+x^3y-y²)/(x^4y-x²y²-xy^3)
4) 3/(c-d) - 6d/(c²-d²) + 3/(d+c) = 6/(c+d)
5)6/(2x-4y) - (x+2y)/(x²-4y²) = 2/(x-2y)
6) (5x+1)/(x²-9) = 7/(3x+9)+8/(3x-9)
7) -2x/(x-y) = 2x/(y-x)
8)(-2x^4 y³z)/(-16x²z^6)= (x²y³)/(8z^5)
9) (3x²-27)/(4x²+24x+36) = (3x-9)(4x+12)
10) a²-2a²+1 = (1-a)(1+a)
11) 4a²+4a+1-4b² = (2a-2b+1)(2a+2b+1)
12) x(x+2)/(x+7)(2x-3) = (x²+2x)/(2x²+11x-21)
13) (4+x)/(3x²+12x) = 1/(3x)
14) 2x^4 - 32 = 2(x-2)(x+2)(x²+4)
15) 6a^4 c³ + 12a³c³ + 6a²c³ =6a² (a+1)² c³