Change the sign of each term of the expression that is to be subtracted and then add.
(i) Term to be subtracted = 5x
Changing the sign of each term of the expression gives -5x.
On adding:
2x+(-5x) = 2x-5x
= (2-5)x
= -3x
(ii) Term to be subtracted = -xy
Changing the sign of each term of the expression gives xy.
On adding:
6xy+xy
= (6+1)xy
= 7xy
(iii) Term to be subtracted = 3a
Changing the sign of each term of the expression gives -3a.
On adding:
5b+(-3a)
= 5b-3a
(iv) Term to be subtracted = -7x
Changing the sign of each term of the expression gives 7x.
On adding:
9y+7x
(v) Term to be subtracted = 10x2
Changing the sign of each term of the expression gives -10x2.
On adding:
−7x2 + (-10x2) = −7x2 −10x2
= (−7−10)x2
= −17x2
(vi) Term to be subtracted = a2 − b2
Changing the sign of each term of the expression gives -a2 + b2.
On adding:
b2 − a2 + (-a2 + b2) = b2 − a2 -a2 + b2
= (1+1)b2 +(−1-1) a2
= 2b2 − 2a2