the respond is C. you may discover by using inspection that for the time of the format (a+b)(c+d) - the FOIL technique - your b and d will multiply to -80 one, so 9 and -9 could stand out on your strategies. it additionally must be obvious that the a and c will multiply to 49x², so 7x and 7x could stand out on your strategies. After that, the rest style of falls into place. you may verify the respond by using going backwards. (7x+9)(7x-9) F-First 7x*7x=49x² O-Outter 7x*-9=-sixty 3 I-inner 9*7x=63x L-final 9*-9=-80 one Now upload all of them at the same time: 49x²+63x-63x-80 one 49x²-80 one Yep!
this is also from of perfect square
It is same principle of just x^2
Do not be fool when you see16x remember all this perfect square 4,9,16,25,36,49
16x^2-9
=(4x-3)(4x+3) is the answer
i am going to do another example
9x^2-49
=(3x+7)(3x-7)
Play around with perfect square until you get it