若(x-y+1)²;与丨2x+y-7丨的值互为相反数,则x²-3xy+2y²的值为

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若(x-y+1)²;与丨2x+y-7丨的值互为相反数,则x²-3xy+2y²的值为若(x-y+1)²;与丨2x+y-7丨的值互为相反数,则x²-3xy

若(x-y+1)²;与丨2x+y-7丨的值互为相反数,则x²-3xy+2y²的值为
若(x-y+1)²;与丨2x+y-7丨的值互为相反数,则x²-3xy+2y²的值为

若(x-y+1)²;与丨2x+y-7丨的值互为相反数,则x²-3xy+2y²的值为
(x-y+1)²+丨2x+y-7丨=0
(x-y+1)²=0
丨2x+y-7丨=0
x-y+1=0
2x+y-7=0
x-y=-1
2x+y=7
3x=6
x=2
y=x+1=2+1=3
x²-3xy+2y²
=2²-3*2*3+2*3²
=4-18+18
=4