Question

18.Oblicz wartości liczbowe podanych sum algebraicznych dla x= - 1 y= 0,1
a)
4(5y+1)(1-5y)-5(4x+1)(1-4x)
b)
(x+2y)²+(2x-y)²-5(x+y)(x+y)
w a ma wyjść 78
a w b 0,1

Answer 1

X= - 1 y= 0,1

a)
4(5y+1)(1-5y)-5(4x+1)(1-4x)=(20y+4)(1-5y)-(20x+5)(1-4x)=20y-100y²+4-20y-(20x-80x²+5-20x)=20y-100y²+4-20y-20x+80x²-5+20x=-100y²-1+80x²

-100y²-1+80x²=-100*(0,1)²-1+80*(-1)²=-100*0,01-1+80*1=-1-1+80=78

b)
(x+2y)²+(2x-y)²-5(x+y)(x+y)=x²+4y²+4xy+4x²+y²-4xy-(5x+5y)(x+y)=x²+4y²+4xy +4x²+y²-4xy-(5x²+5xy+5xy+5y²)=x²+4y²+4xy+4x²+y²-4xy-5x²-5xy-5xy-5y²=-10xy

-10xy=-10*(-1)*0,1=1