a) S_day = \(\dfrac{1}{2}\).c.d = \(\dfrac{1}{2}\).4.3.3,18= 19,08 (cm²)      (dt xung quanh )

S = 9+19,08 =28,08 (cm²)       (dt vai phu bon phia va trai nen dat cho leu)

b) Do 28,08 ≥ 20 so tien mua vai dc giam gia 5% tren hoa don

vay so tien mua vai la :

28,08.15 000.(100% - 5%) = 400140 ( dong)

a) D = 360^o - ( A + B + C ) = 360 - ( 102^o + 102⁰ + 102^o ) = 54^o

ΔOAB vuong tai O, theo ding li pythagore ta co :

OB² = AB² -OA² = 17,5² -187,11 = 119,14 

do dos OB = \(\sqrt{119,14}\) ≈ 10,9 cm

suy ra BD = OB + OD = 10,9 + 26,7 = 37,6

a) (-12x¹³ y¹⁵+6x¹⁰y¹⁴):(-3x¹⁰ y¹⁴)

= (-12x¹³ y¹⁵ ) :(-3x¹⁰ y¹⁴ )+(6x¹⁰ y¹⁴ ):(-3x¹⁰ y¹⁴)

= 4x3 y-2

b) (x-y) (x² - 2x +y) - x³ + x² y

= x (x² - 2x + y ) - y (x² - 2x + y) - x³ + x² y

= x³ - 2x² + xy - x²y + 2xy - y² - x³ + x^2y

= -2x² + 3xy - y² 

a) xy + y2 -x-y 

=(xy+y2) - (x+y )

=y (x+y)-(x+y)

=(x+y)(y-1)

b) (x2 y2 -8)2 -1

=(x2 y2 -8-1)(x2 y2 -8+1)

=(x2 y2 -9)(x2 y2 -7)

=(xy-3)(xy+3)(x2 y2 -7)

=(x-1)(x+8)