1)2x-5x²=0 2)5x²-20=0 3)7x+3+4x²=0 4)x²-9x+18=0 5)16k²+9-24k=0
1) x(2-5x)=0; x=0. или 2-5x=0; x=2/5. 2) 5x^2= 20; x^2= 4; x= плюс, минус 2 3) D= 49-4*4*3= 1. x(1,2) = (-7+- 1)/2*4; x(1)= -6/8= -3/4; x(2)= -8/8= -1. 4) D= 81-4*18= 9. x(1)= (9+3)/2= 6; x(2)= (9-3)/2= 3. 5) D= 576-576=0 x=24/32=3/4.