Question

Pilnie potrzebne na jutro :) Z góry bardzo,serdecznie dziękuje ;* Doprowadź do najprostszej postaci i oblicz wartość liczbową wyrażeń : a) 3x (1-2x)-(x-1)(x+2)+(4x-2):2 dla x=-2 b) (2a+b)(a+2b)-(2a-3b)(a+b) dla a= - 2/3;b=-1 c) -2(x do kwadratu - 3)+3x(2-x)-(x-3)(4-3x) dla x=-1,2 d) (x-4y)(2x+y)+3x(2y-x)-2x(y+3x) dla x=-0,4; y=-0,3

Answer 1

a) =3x-6x^2-(x^2+x-2)+2x-1=3x-6x^2-x^2-x+2+2x-1=-7x^2+4x+1

dla x= -2

-7x^2+4x+1=-7*4+4*(-2)+1=-28-8+1= -35

 

b) =2a^2 +5ab+2b^2-(2a^2-ab-3b^2)=2a^2+5ab+2b^2-2a^2+ab+3b^2=6ab+5b^2

dla a=-2/3 ,b=-1

6ab+5b^2= 4+5=9

 

c)-2(x^2- 3) + 3x(2-x)-(x-3)(4-3x)=-2x^2+6+6x-3x^2-(-3x^2-12+13x)=-5x^2+6x+6+3x^2+12-13x=-2x^2-7x+18

dla x= -1,2

 

-2x^2-7x+18=23,52

 

d) =2x^2-7xy-4y^2+6xy-3x^2-2xy-6x^2= -7x^2-3xy-4y^2

 

dla x=-0,4 , y=-0,3

 

-7x^2-3xy-4y^2=-1,12-0,36-0,36=-1,84

Answer 2

a)

3x(1-2x)-(x-1)(x+2)+(4x-2):2 =

=3x-6x^2 -*x^2 +2x-x-2)+2x-1 =

=3x-6x^2 -x^2 -x+2+2x-1=

= -7x^2 +4x+1

 

dla x = -2

-7x^2 +4x+1 =

= -7(-2)^2 +4(-2) +1 =

= -7*4 -8+1 =

= -28-8+1 =

=-35

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b)

(2a+b)(a+2b)-(2a-3b)(a+b) =

=2a^2 +4ab+ab+2b^2 -(2a^2 +2ab-3ab-3b^2) =

=2a^2 +5ab+2b^2 -2a^2 +ab+3b^2 =

= 6ab+5b^2

 

dla a = -2/3;  b = -1

6ab+5b^2 =

= 6(-2/3)(-1)+5(-1)^2 =

=4+5 =

= 9

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c)

-2(x^2 -3)+3x(2-x)-(x-3)(4-3x) =

= -2x^2 +6 +6x-3x^2 -(4x-3x^2 -12+9x) =

= -5x^2 +6x+6 -4x+3x^2 +12-9x =

= -2x^2 -7x+18

 

dla x = -1,2

-2x^2 -7x+18 =

= -2(-1,2)^2 -7(-1,2)+18 =

= -2 *1,44 +8,4 +18 =

= -2,88 +26,4 =

= 23,52

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d)

(x-4y)(2x+y)+3x(2y-x)-2x(y+3x) =

=2x^2 +xy -8xy -4y^2 +6xy -3x^2 -2xy -6x^2 =

= -7x^2 -3xy -4y^2

 

dla  x = -0,4; y = - 0,3

-7x^2 -3xy -4y^2 =

= -7(-0,4)^2 -3(-0,4)(-0,3) -4(-0,3)^2 =

= -7*0,16 -3*0,12 -4*0,09 =

= -1,12-0,36-0,36 =

= -1,84

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