7m + 3mn
when m = 3 and n = -4

-15

Step-by-step explanation:

When m=3 and n=-4

So, put the values

7(3)+3(3)(-4)

-> -15

-15

Step-by-step explanation:

= 7(3) + 3(3)(-4)

= 21 + 3(3×-4)

= 21 + 3(-12)

= 21 + -36

= 21-36

= -15

step-by-step explanation:

their are no angles. sorry cant .

step-by-step explanation:

no, her answer is not correct.   we square the lengths of all sides and then determine whether the pythagorean theorem holds here:

9² + 15² = 306.   this is not equal to the square of the longest side ( that square being 395.   answer c is correct.