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If f(x) = 2x2 − 3x + 1, find the value of 2f(0) + f(-1) - 3f(f(0)). 2. If 10x + 10y = 2, then the smallest possible value of (x+y) is

Mathematics

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Answer

B
Graph of f(x) = 2x² − 3x + 1

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Key points of f(x) = 2x² − 3x + 1
Pointxy
y-intercept01
x-intercept0.50
Minimum0.75−0.12
x-intercept10

Step-by-step solution

13 steps

Here are the solutions to the problems:

1. If f(x)=2x2−3x+1f(x) = 2x^2 - 3x + 1, find the value of 2f(0)+f(−1)−3f(f(0))2f(0) + f(-1) - 3f(f(0)).

  1. Calculate f(0)f(0).

    f(0)=2(0)2−3(0)+1=0−0+1=1f(0) = 2(0)^2 - 3(0) + 1 = 0 - 0 + 1 = 1
  2. Calculate f(−1)f(-1).

    f(−1)=2(−1)2−3(−1)+1=2(1)+3+1=2+3+1=6f(-1) = 2(-1)^2 - 3(-1) + 1 = 2(1) + 3 + 1 = 2 + 3 + 1 = 6
  3. Calculate f(f(0))f(f(0)).

    Since f(0)=1f(0)=1, we need to find f(1)f(1).

    f(1)=2(1)2−3(1)+1=2−3+1=0f(1) = 2(1)^2 - 3(1) + 1 = 2 - 3 + 1 = 0
  4. Substitute the calculated values into the expression.

    2f(0)+f(−1)−3f(f(0))=2(1)+6−3(0)=2+6−0=82f(0) + f(-1) - 3f(f(0)) = 2(1) + 6 - 3(0) = 2 + 6 - 0 = 8

    The value is 8.

    The correct option is (B).

    B\boxed{\text{B}}

    2. If log⁡10x+log⁡10y=2\log_{10}x + \log_{10}y = 2, then the smallest possible value of (x+y)(x+y) is

  5. Use the logarithm property log⁡aM+log⁡aN=log⁡a(MN)\log_a M + \log_a N = \log_a (MN).

    log⁡10(xy)=2\log_{10}(xy) = 2
  6. Convert the logarithmic equation to an exponential equation.

    xy=102xy = 10^2 xy=100xy = 100
  7. To find the smallest possible value of x+yx+y for positive xx and yy (since they are arguments of a logarithm), we use the AM-GM inequality, which states that for non-negative numbers aa and bb, a+b2≥ab\frac{a+b}{2} \ge \sqrt{ab}.

    x+y2≥xy\frac{x+y}{2} \ge \sqrt{xy}
  8. Substitute xy=100xy=100 into the inequality.

    x+y2≥100\frac{x+y}{2} \ge \sqrt{100} x+y2≥10\frac{x+y}{2} \ge 10 x+y≥20x+y \ge 20

    The equality holds when x=yx=y. If x=yx=y, then x⋅x=100  ⟹  x2=100x \cdot x = 100 \implies x^2 = 100. Since x>0x>0, x=10x=10. Thus, y=10y=10.
    The smallest value of x+yx+y is 10+10=2010+10=20.

    The correct option is (C).

    C\boxed{\text{C}}

    3. If y=xexy = \sqrt{x} e^x, find dydx\frac{dy}{dx}.

  9. Identify the function as a product of two functions

    u(x)=xu(x) = \sqrt{x} and v(x)=exv(x) = e^x. We will use the product rule for differentiation: ddx(uv)=udvdx+vdudx\frac{d}{dx}(uv) = u\frac{dv}{dx} + v\frac{du}{dx}.

  10. Find the derivative of u(x)=x=x1/2u(x) = \sqrt{x} = x^{1/2}.

    dudx=12x12−1=12x−12=12x\frac{du}{dx} = \frac{1}{2}x^{\frac{1}{2}-1} = \frac{1}{2}x^{-\frac{1}{2}} = \frac{1}{2\sqrt{x}}
  11. Find the derivative of v(x)=exv(x) = e^x.

    dvdx=ex\frac{dv}{dx} = e^x
  12. Apply the product rule.

    dydx=(x)(ex)+(ex)(12x)\frac{dy}{dx} = (\sqrt{x})(e^x) + (e^x)\left(\frac{1}{2\sqrt{x}}\right)
  13. Factor out exe^x and simplify.

    dydx=ex(x+12x)\frac{dy}{dx} = e^x \left(\sqrt{x} + \frac{1}{2\sqrt{x}}\right)

    This matches option (B).

    The correct option is (B).

    B\boxed{\text{B}}
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