1) 4√2+√72-√18=4√2+√36*2-√9*2=4√2+6√2-3√2=7√2
2) 3√2(5√2-√32)=3√2(5√2-√2*16)=3√2(5√2-4√2)=3√2*√2=6
3) (√13+5)(5-√13)=5²-(√13)²=25-13=12
4) (4-5√2)²+√18=4²+(5√2)²-2*4*5√2+√9*2=16+50-40√2+3√2=66-37√2
Х²-(х+3)(х-3)=3х
х²-(х²-3х+3х-9)=3х
х²-(х²-9)=3х
х²-х²+9=3х
9=3х
х=9:3=3
Ответ: х=3
(x-y/2x)² × (4x/x-y +4x/y) = (x²-2xy+y²/4x²) × (4xy+4x² - 4xy/y(x-y)) =
4x²(x-y)² / 2xy(x-y) = 2x(x-y) / y