Evaluate (3 a^2 (b c))/(2 b)-3 c-(b c)/a where a = -2, b = 3 and c = -5:
3 a^2 (b c)/(2 b)-3 c-(b c)/a = 3×(-2)^2×(-5×3)/(2×3)--5×3-(-5×3)/(-2)
3×(-2)^2×(3 (-5))/(2×3) = (3 (-5) 3×(-2)^2)/(2×3):
(-5×3×3×(-2)^2)/(2×3)--5×3-(-5×3)/(-2)
(3 (-5) 3×(-2)^2)/(2×3) = 3/3×(-5×3×(-2)^2)/2 = (-5×3×(-2)^2)/2:
(-5×3×(-2)^2)/2--5×3-(-5×3)/(-2)
(-2)^2 = 4:
(-5×3×4)/2--5×3-(-5×3)/(-2)
4/2 = (2×2)/2 = 2:
-5×3×2--5×3-(-5×3)/(-2)
3 (-5) = -15:
-5×3×2--5×3--15/(-2)
The sign of (-15)/(-2) is positive, so (-15)/(-2) = 1×15/2:
-5×3×2--5×3-15/2
-5×3 = -15:
-15×2--5×3-15/2
-15×2 = -30:
-30--5×3-15/2
-3 (-5) = 15:
-30+15-15/2
Put -30+15-15/2 over the common denominator 2. -30+15-15/2 = (2 (-30))/2+(2×15)/2-(15)/2:
(-30×2)/2+(2×15)/2-(15)/2
2 (-30) = -60:
-60/2+(2×15)/2-(15)/2
2×15 = 30:
(-60)/2+30/2-(15)/2
-60/2+30/2-15/2 = (-60+30-15)/2:
(-60+30-15)/2
-60+30-15 = 30-(60+15):
30-(60+15)/2
(30-75)/2
30-75 = -(75-30):
-(75-30)/2
Answer: |(-45)/2
Learn how to use brackets, so that there is no ambiguity as to you want.
This could mean:(3a^2bc)/(2b) -3c - bc/a, or could mean:(3a^2bc)/(2b-3c) - bc/a, or could mean:
(3a^2bc) / [(2b-3c) - (bc/a)]. All these might or will give you different answers. So, don't be surprised if you get a different answer from what you expect, or is in your book.
