Question

Efectuati calculele .
a) (3x + 1)(4x-5)-(6x-11)(2x+5) =
b) $2x[(-2 x^{2} )-(x+2)(x-3)]-5x( x^{2} -3)$ =
c) (x+1)[3(x+2)-2(x-1)]-4(x+2)=
d) $(x-2)[4(x+5)-3(x+6)]-x(x-4)$=

Answer 1

$a) (3x + 1)(4x-5)-(6x-11)(2x+5)=12 x^{2} -15x+4x-5-(12 x^{2}\\+30x-22x-55)=12 x^{2} -11x-5-12 x^{2} -30x+22x+55=\\=50-19x$
[tex]b) 2x[(-2 x^{2} )-(x+2)(x-3)]-5x( x^{2} -3)=2x[-2x^2-(x^2-3x+\\+2x-6)]-5x^3+15x=2x(-2x^2- x^{2} +3x-2x+6)-5x^3+15x=\\=2x(-3x^2+x+6)-5x^3+15x=-6x^3+2x^2+12x-5x^3+15x=\\=-11x^3+2x^2+17x=x(-11x^2+2x+17)\\ c) (x+1)[3(x+2)-2(x-1)]-4(x+2)=(x+1)[3x+6-2x+2]=\\= (x+1)(x+8)= x^{2} +8x+x+8= x^{2} +9x+8\\ d) (x-2)[4(x+5)-3(x+6)]-x(x-4)=(x-2)[4x+20-3x-18]\\=(x-2)(x+2)=x^2-2^2= x^{2} -4[/tex]