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If m = -9 and n = 13, find the value of 25m2 + 40mn +16n2
Question

If m = -9 and n = 13, find the value of 25m2 + 40mn +16n2

A.

64

B.

49

C.

81

D.

100

Correct option is B

Given:

m = -9, n = 13.

Solution:

25m2+40mn+16n2=(5m+4n)225m^2 + 40mn + 16n^2 = (5m + 4n)^2 

Then, 

5m+4n=5(9)+4(13)=45+52=75m + 4n = 5(-9) + 4(13) = -45 + 52 = 7 

So, 

(5m+4n)2=72=49.(5m + 4n)^2 = 7^2 = 49. ​​

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