Addition of Algebraic Expressions
Q. Find the sum of the following expressions:
1. 7xy+5yz−3zx
2. 4yz+9zx−4y
3. −3xy+5x−2xy
Options:
(a) 5x−4y−2xy−9yz+6zx
(b) 5x−4y+6xy+9yz+6zx
(c) 5x−4y+6xy−9yz−6zx
(d) 5x−4y+2xy+9yz+6zx
Line Trick : Just combine like terms
Just combine (7xy−3xy−2xy)+(5yz+4yz)+(−3zx+9zx)+(−4y)+(5x)
= 2xy+9yz+6zx−4y+5x (Re-arrange)
Ans: (d) 5x - 4y + 2xy + 9yz + 6zx
Q. Subtract 12x-z from the sum of 2x-3y+7z and 4z-5x.
Soln,
(12x−z)−(−3x−3y+11z), Here 2x−3y+7z+4z−5x = −3x−3y+11z
Change signs of the second bracket
−(−3x−3y+11z) = 3x+3y−11z
Add like terms
- x terms: 12x+3x = 15x
- y terms: 0+3y = 3y
- z terms: -z-11z = -12z
Ans:15x+3y-12z