(x + a) (x + b) = x² + (a + b) x + ab
75 * 77=
=(70+5)(70+7)
=70²+(5+7)*70+5*7
=4900+12*70+35
=4900+840+35
=5775
To solve for <em>x</em>, we must first isolate the term containing <em>x</em> which in this problem is 5x.
Since 10 is being added to 5x, we subtract 10 from both sides of the equation to isolate the 5x.
On the left, the +10 and -10 cancel out and on the right, 20 - 10 is 10 and we have 5x = 10.
Now we can finish things off by just dividing both sides of the equation by 5. On the left the 5's cancel and on the right, 10 divided by 5 is 2 so <em>x = 2</em>.
You'd want to buy the 4 by 5 and the 11 by 14 because if you times 4 by 3 and 5 by 3, the answer would be 12 by 15 which is the closet or the most similar pair
