Question

dau coroana
1)a)21²-20²
b)3,5²-2,5²
c)114²-14²
d)1990²-990²
2)Descompuneti in factori
a)x²/4-y²
b)4/9-x²
c)1/36x²-25y²
d)x²-81/64
e)a²/4-16b²/121
f)4/49a²b²c²-1
g)225/16x²-168/196y²
h)x²/4y²-25z²/9t²
i)361x²-1/289 a²

Answer 1

1) a)21²-20²=(21-20)(21+20)= 1 * 41 = 42
    b)3,5²-2,5²=(3,5-2,5)(3,5+2,5)=1 * 6 = 6
    c)114²-14²=(114-14)(114+14)=100 * 128= 12800
    d)1990²-990²=(1990-990)(1990+990)=1000 * 2980=2980000

2.a)x²/4-y²= (x/2-y)(x/2+y)
  b)4/9-x²=(2/3-x)(2/3+x)
  c)1/36x²-25y²=( 1/6x- 5y)(1/6x + 5y)
  d)x² -81/64=(x-9/8)(x+9/8)
  e)a²/4-16b²/121=(a/2-4b/11)(a/2 + 4b/11)
  f)4/49a²b²c²-1=(2/7abc-1)(2/7abc +1)
  g)225/16x²-169/196y²=(15/4x-13/14y)(15/4x+13/14y)
  h)x²/4y²-25z²/9t²=(x/2y-5z/3t)(x/2y+5z/3t)
  i)361x²-1/289 a²=(19x-1/17a)(19x+1/17 a)