Zad. 1
h^2+8^2=9^2
h=\sqrt{81-64}
h=\sqrt{17}
c^2=h^2+2^2
c^2=\sqrt{17}^2+4
c=\sqrt{17+4}=\sqrt{21}
P=\frac{a+b}{2}*h
P=\frac{16*\sqrt{17}}{2}=8\sqrt{17}
Ob=16+6+2\sqrt{21}=22+2\sqrt{17} .
Zad. 2
4x(5x-8)-8(x+5)(3x-8)=
=20x^2-32x-8(3x^2-8x+15x-40)=
=20x^2-32x-24x^2+64x-120x+320=-4x^2-88x+320
Zad. 3
a)
35ab^3-21ba^4=7ab(5b^2-3a^3)
b)
256x^4-81=(16x^2-9)(16x^2+9)=
=(4x-3)(4x+3)(16x^2+9)
Zad. 4
x(4x+7)(x^2-4)=0
x=0 lub 4x+7=0 lub x^2-4=0
x=0 lub 4x=-7 lub (x-2)(x+2)=0
x=0 lub x=-\frac{7}{4} lub =2 lub x=-2