question_answer 19)

Simplify these expressions and find their value if \[x=3,a=-1,b=-2\]. (i) \[3x-5-x+9\]                  (ii) \[2-8x+4x+4\]             (iii) \[3a+5-8a+1\]            (iv) \[10-3b-4-5b\] (v) \[2a-2b-4-5+a.\]

Answer:

                (i) \[3x-5-x+9=3x-x+9-5\]                                             \[\left| \text{rearranging terms} \right.\]                 \[=2x+4=2(3)+4\]                 \[=6+4=10\]                 (ii) \[2-8x+4x+4=4x-8x+2+4\]                      \[\left| \text{rearranging terms} \right.\]                 \[=-4x+6=-4(3)+6\] \[=-12+6=-6\].                 (iii) \[3a+5-8a+1=3a-8a+5+1\]                     \[\left| \text{rearranging terms} \right.\]                 \[=-5a+6=-5(-1)+6\] \[=5+6=11\].                 (iv) \[10-3b-4-5b=-3b-5b+10-4\]                                \[\left| \text{rearranging terms} \right.\] \[=-8b+6=-8(-2)+6\]       \[=16+6=22.\]                 (v) \[2a-2b-4-5+a=2a+a-2b-4-5\]               \[\left| \text{rearranging terms} \right.\]                 \[=3a-2b-9\]                       \[=3(-1)-2(-2)-9\] \[=-3+4-9=4-3-9\] \[=4-12=-8\]