Subtract the sum of 3l-4m-7n2 and 2l+3m-4n2 from the sum of 9l+2m-3n2 and -3l+m+4n2………

Subtract the sum of 3l-4m-7n2 and 2l+3m-4n2 from the sum of 9l+2m-3n2 and -3l+m+4n2………

Sum of 9l + 2m – 3n2 and -3l + n + 4n2


= 9l + 2m – 3n2 + (-3l + m + 4n2)


= 9l – 3l + 2m + m – 3n2 + 4n2


= 6l + 3m + n2 (i)


Sum of 3l – 4m – 7n2 and 2l + 5m – 4n2


= 3l – 4m – 7n2 + 2l + 5m – 4n2


= 5l – m – 11n2 (ii)


Subtract (i) and (ii), we get


= 6l + 3m + n2 – (5l – m – 11n2)


= 6l – 5l + 3m + m + n2 + 12n2


= l + 4m + 13n2


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