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

AcademicMathematicsNCERTClass 7

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 $b=-2$

$=3(-1) - 2(-2) - 9$

$=-3+4 -9$

$=-8$
raja
Updated on 10-Oct-2022 13:38:20

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