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Vector Algebra

Question
CBSEENMA12032725

Find the area of the region enclosed by the parabola x2 = y, the line y = x + 2 and the x-axis.
OR
Draw the rough sketch and find the area of the region:
{(x, y): x2 < y < x + 2}

Solution

The equation of parabola is
x2 = y    ...(1)
The equation of line is
y = x + 2    ...(2)
From (1) and (2), we get,
x2 = x + 2
∴ x2 - x - 2 = 0

⇒ (x - 2) (x + 1) = 0 ⇒    x = 2, -1
∴    from (2), y= 2 + 2, -1 +2 = 4, 1
∴  parabola (1) meets line (2) in two points A (2, 4) and B (-1. 1).
From A. draw AM ⊥ x-axis and from B. draw BN ⊥ x-axis.
Required area = Area AOB
integral subscript negative 1 end subscript superscript 2 left parenthesis straight x plus 2 minus straight x squared right parenthesis space dx space equals space open square brackets straight x squared over 2 plus 2 straight x minus straight x cubed over 3 close square brackets subscript negative 1 end subscript superscript 2
equals space open parentheses 4 over 2 plus 4 minus 8 over 3 close parentheses space minus space open parentheses 1 half minus 2 plus 1 third close parentheses space equals space 2 plus 4 minus 8 over 3 minus 1 half plus 2 minus 1 third equals 9 over 2 space sq. space units.

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