2x²+5x-18=2(x²+5/2x-9)=2(x²+2·x·5/4+25/16-25/16-9)=2((x+5/4)²-9 25/16)=
2((x+5/4)²-10 9/16)= 2(x+5/4)²- 21 1/8.
2x²+5x-18=2(x²+5/2x-9)=2(x²+2·x·5/4+25/16-25/16-9)=2((x+5/4)²-9 25/16)=
2((x+5/4)²-10 9/16)= 2(x+5/4)²- 21 1/8.