a)
(5+x)(x−2)+(7+x)(2x−1)=5⋅x−5⋅2+x⋅x−x⋅2+7⋅2x−7⋅1+x⋅2x−x⋅1=5x−10+x2−2x+14x−7+2x2−x=
=3x2+16x−17=
=3⋅(−3)2+16⋅(−3)−17=
=27−48−17=−38
b)
(y−3)(4−y)−(8+y)(9−y)=y⋅4−y⋅y−3⋅4+3⋅y−(8⋅9−8⋅y+y⋅9−y⋅y)=
=4y−y2−12+3y−(72−8y+9y−y2)=
=7y−y2−12−(72 +y−y2)=
=7y−y2−12−72 −y+y2=
=6y−84=
=6⋅2,5−84=
=15−84=−69
c)
4−x(2+x)−3−3(x2−6x−5)=4−2x−x⋅x−3−3x2+3⋅6x+3⋅5=
=4−2x−x2−3−3x2+18x+15=
=−4x2+16x+16=
=−4⋅(32)2+16⋅32+16=
=−4⋅94+332+16=
=−916+996+16=
=980 +16=
=898+16=2498
d)
2(x−5)(y+4)−3(2x+1)(5−y)=
=2(xy+4x−5y−20)−3(10x−2xy+5−y)=
=2xy +8x−10y−40−30x+6xy−15+3y=
=8xy −7y −22x −55 =
=8⋅4⋅1−7⋅1−22⋅4−55=
=32−7−88−55=
=−118
e)
12ab−3(a−2b)(a+2b)+2(a−3b)=
=12ab−3(a2+2ab−2ab−4b2)+2a−6b=
=12ab−3(a2−4b2)+2a−6b=
=12ab−3a2+12b2+2a−6b=
=12⋅32⋅(−3)−3⋅(32)2+12⋅(−3)2+2⋅32−6⋅(−3)=
=−366−3⋅18+12⋅3+62+63=
=−366−54+36+62+63=
=−366−18+62+63
f)
5−3(y2−4y+2)+(3y−2)(3y+2)=
=5−3y2+12y−6+3y2+23−23y−4=
=12y −5=
=12 1⋅(−12 15)−5=−5−5=−10
