A) 2x-7=13
2x=20
x=10
B) 3x+4=25
3x=21
x=7
That's a trapezoid,


Answer: 32
But say we didn't know the formula. We can chop out the 4 by 4 square and we have two 45/45/90 triangles side 4 left over, so two 4 by 4 squares,
A = 2(4)(4) = 32
We can think of this as 12 by 4 rectangle with two 4 by 4 right triangles chopped out:
A = 12(4) - 2(1/2)(4)(4) = 48 - 16 = 32
Since it starts at 12 and is increasing by 5 each time, the 70th term will be;
12 + 5(70)
12 + 350
362
362 is the 70th term of the sequence.
Answer:
Ben has mixed up the digit for millions and hundred thousands: he wrote 5 in the place for millions and 6 in the place for hundred thousands, but it should be the other way. I think that he should exchange those two digits in the faulty report.
Sqrt[x] = -x
x= x ^ 2
x - x^2 = 0
-x(x-1)=0
x(x-1)=0
x = 1 or x = 0
sqrt 1 isn not equal to 0
x= 0