Evaluate:
(27² – 23²) + (14² – 6²)
A. 1680
B. 360
C. 80
D. 840
E. 40
We can solve this question quickly if we know the difference of two squares:
a^2 -b^2 = (a-b)(a+b)
Following:
(27^2-23^2) + (14^2-6^2) = (27-23)(27+23) + (14-6)(14+6) =
=4\cdot 50 + 8 \cdot 20 = 200 + 160 = 360
Which gives us the correct answer: (B) 360.
5 Likes
hi natali,i got the diffrence of two squares part, but how did you get 50, and 20 to multiply with 4and 8 respectively, i am confused, thank you for your help!
There is a (not so visible) multiplication sign between parentheses.
1 Like