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Nataliya [291]
3 years ago
14

How to solve 7m + 2n = 21 and 10m + 4n = -10 using substitution. Step by step please and thank you!

Mathematics
1 answer:
ryzh [129]3 years ago
5 0
7m+2n=21
-7m      -7m

<u>2n</u>=<u>21-7m</u> 
2        2

n=<u>21-7m
</u>       2
<u>
</u>10m+4(21-7m/2)= -10
<u />-10m                   -10m

4(21-7m/2)= -10-10m

(84-28m/2)= -10-10m
    x2                x2

84-28m    = -20-20m
+20+28m   +20+28m

<u>104</u> = <u>8m
</u>8         8

m=13

10(13) + 4n = -10
-130              -130

<u>4n</u> = <u>-140
</u>4         4
<u>
</u>n= -35

If anything is unclear please feel free to ask.
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10/ sqrt(2) = 7.1 is the rounded answer.

to double check your work just multiply 7.1 by the square root of 2 and you'll get <em>close</em> to 10. (because the answer is rounded and not exact.)

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Look below

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So I will use an example to try and show you how to do this.

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