Question

# If y = 4x - 5 is a tangent to the curve y2 = px3 + q at (2, 3) then :p = 2, q = -7p = -2, q = 7p = -2, q = -7p =2, q = 7

Solution

## The correct option is A p = 2, q = -7Given (2, 3) lies on y2=px3 + q we get 9 = 8p + q     .....(1) Again y2=px3 + q ⇒ 2y dydx=3px2 ⇒dydx=3px22y ⇒(dydx)(2,3)=12p6 = 2p since y = 4x - 5 is tangent to y2=px3 + q at (2, 3) therefore 2p = 4 ⇒ p = 2. Putting p=2 in equation (1), we get q = -7 Hence p = 2, q = -7.

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