Simplify these expressions and find their values if $x=3,\ a=-1,\ b=-2$
$(i)$. $3x-5-x+9$
$(ii)$. $2-8x+4x+4$
$(iii)$. $3a+5-8a+1$
$(iv)$. $10-3b-4-5b$
$(v)$. $2a-2b-4-5+a$
Given: $(i)$. $3x-5-x+9$
$(ii)$. $2-8x+4x+4$
$(iii)$. $3a+5-8a+1$
$(iv)$. $10-3b-4-5b$
$(v)$. $2a-2b-4-5+a$
To do: To simplify these expressions and find their values if $x=3,\ a=-1,\ b=-2$.
Solution:
$(i)$ $3x-5-x+9$
$=2x+4$
if $x=3$
$=2(3)+4$
$=6+4$
$=10$
$(ii)$. $2-8x+4x+4$
$=-8x+4x+4+2$
$=-4x+6−4x+6$
$=-4(3)+6$ [If $x=3$]
$=-6$
$(iii)$. $3a+5-8a+1$
$=3a-8a+5+1$
$=-5a+6$
$=-5(-1)+6$
$=5+6$
$=11$
$(iv)$. $10-3b-4-5b$
$=6-8b$
$=6-8(-2)$ [$b=-2$]
$=6 - 8(-2)$
$=6+ 16$
$=22$
$(v)$. $2a-2b-4-5+a$
$=2a+a-2b-4-5$
$=3a+2b-9$
If $a=-1$ and $b=-2$
$=3(-1) - 2(-2) - 9$
$=-3+4 -9$
$=-8$
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