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Math Help - Expressing in another form

  1. #1
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    Expressing in another form

    How do you express x^2+5x into the form: a(2x^2+x)+b(3x^2+x)
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    Quote Originally Posted by sleepingpanda View Post
    How do you express x^2+5x into the form: a(2x^2+x)+b(3x^2+x)
    x^2 + 5x = 2a*x^2 + ax + 3bx^2 + bx.
    Compare the coefficient of x^2 and x, and solve the simultaneous equation to find a and b.
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  3. #3
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    when i compare the coefficients of x^2 and x do i compare 3bx^2 to x^2 or 2ax^2 with x^2?
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    Quote Originally Posted by sleepingpanda View Post
    when i compare the coefficients of x^2 and x do i compare 3bx^2 to x^2 or 2ax^2 with x^2?
    No. Collect the coefficients of x^2 in the right hand side and equate it to that of left hand side. You get on equation is a and b. Repeat the same thing for x to get another equation in a and b. Solve these two equations to find a and b.
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    Quote Originally Posted by sa-ri-ga-ma View Post
    No. Collect the coefficients of x^2 in the right hand side and equate it to that of left hand side. You get on equation is a and b. Repeat the same thing for x to get another equation in a and b. Solve these two equations to find a and b.
    Sorry but I'm having trouble understanding, could it be possible if you can solve it step by step?
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  6. #6
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    Quote Originally Posted by sleepingpanda View Post
    Sorry but I'm having trouble understanding, could it be possible if you can solve it step by step?
    Sorry. We are supposed to give the hints, so that you can solve the problem your self. You are not showing any attempt on your part.
    My hint is very clear.
    What is the coefficient of x^2 on right hand side?
    What is coefficients of x^2 on the left hand side?
    Equate them. That is one equation.
    Repeat the same thing for x.
    Show your attempt.
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  7. #7
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    Quote Originally Posted by sa-ri-ga-ma View Post
    Sorry. We are supposed to give the hints, so that you can solve the problem your self. You are not showing any attempt on your part.
    My hint is very clear.
    What is the coefficient of x^2 on right hand side?
    What is coefficients of x^2 on the left hand side?
    Equate them. That is one equation.
    Repeat the same thing for x.
    Show your attempt.
    hmmmm... well the coefficient of x^2 on the left hand side is 1 and the coefficient of x^2 on the right hand side is 2 & 3, would the equation be 1=2ax^2+3bx^2? and for coefficient x it would be 5=a+b?
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  8. #8
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    Quote Originally Posted by sleepingpanda View Post
    hmmmm... well the coefficient of x^2 on the left hand side is 1 and the coefficient of x^2 on the right hand side is 2 & 3, would the equation be 1=2ax^2+3bx^2? and for coefficient x it would be 5=a+b?
    the coefficient of x^2 on the right hand side is 2 & 3
    This is not correct. It should be 2a and 3b.
    So 1 = 2a + 3b.
    Now solve the two equations to find a and b.
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